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 $108.69   7.413%   $116.7472   $116.75   $116.75   $116.70  
  Purchase #2 $168.67   3.128%   $173.946   $173.95   $173.95   $173.90  
  Purchase #3 $165.41   11.489%   $184.414   $184.41   $184.40   $184.40  
  Purchase #4 $221.34   4.822%   $232.013   $232.01   $232.00   $232.00  
  Purchase #5 $138.90   8.673%   $150.9468   $150.95   $150.95   $150.90  
  Purchase #6 $59.36   3.198%   $61.2583   $61.26   $61.25   $61.30  
  Purchase #7 $178.65   11.192%   $198.6445   $198.64   $198.65   $198.60  
  7 purchase totals = $1,041.02       $1,117.9698   $1,117.97   $1,117.95   $1,117.80