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 $186.66   4.339%   $194.7592   $194.76   $194.75   $194.80  
  Purchase #2 $55.98   12.142%   $62.7771   $62.78   $62.80   $62.80  
  Purchase #3 $45.98   3.345%   $47.518   $47.52   $47.50   $47.50  
  Purchase #4 $121.49   6.117%   $128.9215   $128.92   $128.90   $128.90  
  Purchase #5 $217.99   11.476%   $243.0065   $243.01   $243.00   $243.00  
  Purchase #6 $108.36   6.204%   $115.0827   $115.08   $115.10   $115.10  
  Purchase #7 $203.60   9.174%   $222.2783   $222.28   $222.30   $222.30  
  7 purchase totals = $940.06       $1,014.3433   $1,014.35   $1,014.35   $1,014.40