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 $188.27   7.395%   $202.1926   $202.19   $202.20   $202.20  
  Purchase #2 $107.70   7.142%   $115.3919   $115.39   $115.40   $115.40  
  Purchase #3 $179.52   4.699%   $187.9556   $187.96   $187.95   $188.00  
  Purchase #4 $51.25   12.282%   $57.5445   $57.54   $57.55   $57.50  
  Purchase #5 $235.52   3.577%   $243.9446   $243.94   $243.95   $243.90  
  Purchase #6 $164.39   6.168%   $174.5296   $174.53   $174.55   $174.50  
  Purchase #7 $65.61   10.243%   $72.3304   $72.33   $72.35   $72.30  
  7 purchase totals = $992.26       $1,053.8892   $1,053.88   $1,053.95   $1,053.80