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 $177.69   10.310%   $196.0098   $196.01   $196.00   $196.00  
  Purchase #2 $214.76   11.217%   $238.8496   $238.85   $238.85   $238.80  
  Purchase #3 $214.25   13.573%   $243.3302   $243.33   $243.35   $243.30  
  Purchase #4 $27.52   3.669%   $28.5297   $28.53   $28.55   $28.50  
  Purchase #5 $125.28   9.435%   $137.1002   $137.10   $137.10   $137.10  
  Purchase #6 $67.82   9.121%   $74.0059   $74.01   $74.00   $74.00  
  Purchase #7 $166.59   6.358%   $177.1818   $177.18   $177.20   $177.20  
  7 purchase totals = $993.91       $1,095.0072   $1,095.01   $1,095.05   $1,094.90