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 $194.82   5.211%   $204.9721   $204.97   $204.95   $205.00  
  Purchase #2 $224.84   3.515%   $232.7431   $232.74   $232.75   $232.70  
  Purchase #3 $109.91   3.441%   $113.692   $113.69   $113.70   $113.70  
  Purchase #4 $102.47   3.674%   $106.2347   $106.23   $106.25   $106.20  
  Purchase #5 $46.77   4.107%   $48.6908   $48.69   $48.70   $48.70  
  Purchase #6 $36.79   6.843%   $39.3075   $39.31   $39.30   $39.30  
  Purchase #7 $37.75   6.860%   $40.3397   $40.34   $40.35   $40.30  
  7 purchase totals = $753.35       $785.9799   $785.97   $786.00   $785.90