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 $168.33   4.761%   $176.3442   $176.34   $176.35   $176.30  
  Purchase #2 $244.52   7.502%   $262.8639   $262.86   $262.85   $262.90  
  Purchase #3 $143.59   3.494%   $148.607   $148.61   $148.60   $148.60  
  Purchase #4 $72.70   11.444%   $81.0198   $81.02   $81.00   $81.00  
  Purchase #5 $216.82   13.362%   $245.7915   $245.79   $245.80   $245.80  
  Purchase #6 $235.66   11.284%   $262.2519   $262.25   $262.25   $262.30  
  Purchase #7 $247.80   6.121%   $262.9678   $262.97   $262.95   $263.00  
  7 purchase totals = $1,329.42       $1,439.8461   $1,439.84   $1,439.80   $1,439.90