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 $58.40   9.618%   $64.0169   $64.02   $64.00   $64.00  
  Purchase #2 $83.86   11.848%   $93.7957   $93.80   $93.80   $93.80  
  Purchase #3 $162.52   8.269%   $175.9588   $175.96   $175.95   $176.00  
  Purchase #4 $141.95   4.731%   $148.6657   $148.67   $148.65   $148.70  
  Purchase #5 $82.96   5.710%   $87.697   $87.70   $87.70   $87.70  
  Purchase #6 $247.69   3.738%   $256.9487   $256.95   $256.95   $256.90  
  Purchase #7 $216.86   4.341%   $226.2739   $226.27   $226.25   $226.30  
  7 purchase totals = $994.24       $1,053.3567   $1,053.37   $1,053.30   $1,053.40