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 $176.91   9.661%   $194.0013   $194.00   $194.00   $194.00  
  Purchase #2 $129.28   4.290%   $134.8261   $134.83   $134.85   $134.80  
  Purchase #3 $53.35   4.203%   $55.5923   $55.59   $55.60   $55.60  
  Purchase #4 $228.70   6.339%   $243.1973   $243.20   $243.20   $243.20  
  Purchase #5 $8.52   11.745%   $9.5207   $9.52   $9.50   $9.50  
  Purchase #6 $31.80   4.123%   $33.1111   $33.11   $33.10   $33.10  
  Purchase #7 $31.46   5.820%   $33.291   $33.29   $33.30   $33.30  
  7 purchase totals = $660.02       $703.5398   $703.54   $703.55   $703.50