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 $216.75   3.827%   $225.045   $225.05   $225.05   $225.00  
  Purchase #2 $118.76   12.773%   $133.9292   $133.93   $133.95   $133.90  
  Purchase #3 $232.67   3.707%   $241.2951   $241.30   $241.30   $241.30  
  Purchase #4 $184.85   11.801%   $206.6641   $206.66   $206.65   $206.70  
  Purchase #5 $135.46   7.189%   $145.1982   $145.20   $145.20   $145.20  
  Purchase #6 $166.76   3.689%   $172.9118   $172.91   $172.90   $172.90  
  Purchase #7 $124.60   11.372%   $138.7695   $138.77   $138.75   $138.80  
  7 purchase totals = $1,179.85       $1,263.8129   $1,263.82   $1,263.80   $1,263.80