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 $87.35   9.261%   $95.4395   $95.44   $95.45   $95.40  
  Purchase #2 $243.25   4.539%   $254.2911   $254.29   $254.30   $254.30  
  Purchase #3 $149.27   6.145%   $158.4426   $158.44   $158.45   $158.40  
  Purchase #4 $233.62   4.355%   $243.7942   $243.79   $243.80   $243.80  
  Purchase #5 $177.51   10.766%   $196.6207   $196.62   $196.60   $196.60  
  Purchase #6 $70.55   4.241%   $73.542   $73.54   $73.55   $73.50  
  Purchase #7 $164.83   10.129%   $181.5256   $181.53   $181.55   $181.50  
  7 purchase totals = $1,126.38       $1,203.6557   $1,203.65   $1,203.70   $1,203.50