Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $95.82   8.741%   $104.1956   $104.20   $104.20   $104.20  
  Purchase #2 $145.39   11.108%   $161.5399   $161.54   $161.55   $161.50  
  Purchase #3 $166.57   12.843%   $187.9626   $187.96   $187.95   $188.00  
  Purchase #4 $159.86   7.182%   $171.3411   $171.34   $171.35   $171.30  
  Purchase #5 $166.33   3.829%   $172.6988   $172.70   $172.70   $172.70  
  Purchase #6 $189.61   5.651%   $200.3249   $200.32   $200.30   $200.30  
  Purchase #7 $120.81   4.507%   $126.2549   $126.25   $126.25   $126.30  
  7 purchase totals = $1,044.39       $1,124.3178   $1,124.31   $1,124.30   $1,124.30