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 $85.77   7.279%   $92.0132   $92.01   $92.00   $92.00  
  Purchase #2 $216.52   9.320%   $236.6997   $236.70   $236.70   $236.70  
  Purchase #3 $31.52   13.840%   $35.8824   $35.88   $35.90   $35.90  
  Purchase #4 $233.55   7.412%   $250.8607   $250.86   $250.85   $250.90  
  Purchase #5 $196.48   11.781%   $219.6273   $219.63   $219.65   $219.60  
  Purchase #6 $179.45   8.325%   $194.3892   $194.39   $194.40   $194.40  
  Purchase #7 $177.31   12.791%   $199.9897   $199.99   $200.00   $200.00  
  7 purchase totals = $1,120.60       $1,229.4622   $1,229.46   $1,229.50   $1,229.50