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 $62.33   8.216%   $67.451   $67.45   $67.45   $67.50  
  Purchase #2 $242.65   10.289%   $267.6163   $267.62   $267.60   $267.60  
  Purchase #3 $10.56   8.702%   $11.4789   $11.48   $11.50   $11.50  
  Purchase #4 $147.35   9.407%   $161.2112   $161.21   $161.20   $161.20  
  Purchase #5 $219.95   8.462%   $238.5622   $238.56   $238.55   $238.60  
  Purchase #6 $205.42   11.107%   $228.236   $228.24   $228.25   $228.20  
  Purchase #7 $146.41   13.231%   $165.7815   $165.78   $165.80   $165.80  
  7 purchase totals = $1,034.67       $1,140.3371   $1,140.34   $1,140.35   $1,140.40