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 $7.52   6.705%   $8.0242   $8.02   $8.00   $8.00  
  Purchase #2 $184.94   9.715%   $202.9069   $202.91   $202.90   $202.90  
  Purchase #3 $236.39   13.588%   $268.5107   $268.51   $268.50   $268.50  
  Purchase #4 $208.61   5.129%   $219.3096   $219.31   $219.30   $219.30  
  Purchase #5 $150.51   13.435%   $170.731   $170.73   $170.75   $170.70  
  Purchase #6 $243.69   9.540%   $266.938   $266.94   $266.95   $266.90  
  Purchase #7 $65.38   6.494%   $69.6258   $69.63   $69.65   $69.60  
  7 purchase totals = $1,097.04       $1,206.0462   $1,206.05   $1,206.05   $1,205.90