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 $219.96   9.572%   $241.0146   $241.01   $241.00   $241.00  
  Purchase #2 $68.42   11.328%   $76.1706   $76.17   $76.15   $76.20  
  Purchase #3 $16.92   12.190%   $18.9825   $18.98   $19.00   $19.00  
  Purchase #4 $68.70   6.529%   $73.1854   $73.19   $73.20   $73.20  
  Purchase #5 $220.49   7.633%   $237.32   $237.32   $237.30   $237.30  
  Purchase #6 $216.95   7.187%   $232.5422   $232.54   $232.55   $232.50  
  Purchase #7 $182.33   6.473%   $194.1322   $194.13   $194.15   $194.10  
  7 purchase totals = $993.77       $1,073.3475   $1,073.34   $1,073.35   $1,073.30