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 $91.68   4.272%   $95.5966   $95.60   $95.60   $95.60  
  Purchase #2 $166.33   9.464%   $182.0715   $182.07   $182.05   $182.10  
  Purchase #3 $156.79   6.407%   $166.8355   $166.84   $166.85   $166.80  
  Purchase #4 $143.92   6.340%   $153.0445   $153.04   $153.05   $153.00  
  Purchase #5 $95.55   7.380%   $102.6016   $102.60   $102.60   $102.60  
  Purchase #6 $159.54   12.374%   $179.2815   $179.28   $179.30   $179.30  
  Purchase #7 $216.30   4.543%   $226.1265   $226.13   $226.15   $226.10  
  7 purchase totals = $1,030.11       $1,105.5577   $1,105.56   $1,105.60   $1,105.50