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 $58.76   7.185%   $62.9819   $62.98   $63.00   $63.00  
  Purchase #2 $143.37   6.147%   $152.183   $152.18   $152.20   $152.20  
  Purchase #3 $53.36   8.722%   $58.0141   $58.01   $58.00   $58.00  
  Purchase #4 $116.29   13.118%   $131.5449   $131.54   $131.55   $131.50  
  Purchase #5 $97.35   5.306%   $102.5154   $102.52   $102.50   $102.50  
  Purchase #6 $219.48   12.200%   $246.2566   $246.26   $246.25   $246.30  
  Purchase #7 $85.71   6.190%   $91.0154   $91.02   $91.00   $91.00  
  7 purchase totals = $774.32       $844.5113   $844.51   $844.50   $844.50