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 $82.82   11.445%   $92.2987   $92.30   $92.30   $92.30  
  Purchase #2 $165.72   4.422%   $173.0481   $173.05   $173.05   $173.00  
  Purchase #3 $118.76   6.254%   $126.1873   $126.19   $126.20   $126.20  
  Purchase #4 $116.85   4.346%   $121.9283   $121.93   $121.95   $121.90  
  Purchase #5 $96.94   6.201%   $102.9512   $102.95   $102.95   $103.00  
  Purchase #6 $219.72   11.586%   $245.1768   $245.18   $245.20   $245.20  
  Purchase #7 $126.54   13.849%   $144.0645   $144.06   $144.05   $144.10  
  7 purchase totals = $927.35       $1,005.6549   $1,005.66   $1,005.70   $1,005.70