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 $215.69   9.249%   $235.6392   $235.64   $235.65   $235.60  
  Purchase #2 $24.68   5.443%   $26.0233   $26.02   $26.00   $26.00  
  Purchase #3 $71.94   3.264%   $74.2881   $74.29   $74.30   $74.30  
  Purchase #4 $142.68   4.659%   $149.3275   $149.33   $149.35   $149.30  
  Purchase #5 $186.50   13.124%   $210.9763   $210.98   $211.00   $211.00  
  Purchase #6 $96.30   8.142%   $104.1407   $104.14   $104.15   $104.10  
  Purchase #7 $190.35   6.463%   $202.6523   $202.65   $202.65   $202.70  
  7 purchase totals = $928.14       $1,003.0474   $1,003.05   $1,003.10   $1,003.00