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 $58.82   3.348%   $60.7893   $60.79   $60.80   $60.80  
  Purchase #2 $118.67   11.263%   $132.0358   $132.04   $132.05   $132.00  
  Purchase #3 $205.57   4.309%   $214.428   $214.43   $214.45   $214.40  
  Purchase #4 $138.73   12.419%   $155.9589   $155.96   $155.95   $156.00  
  Purchase #5 $205.39   4.262%   $214.1437   $214.14   $214.15   $214.10  
  Purchase #6 $174.39   4.749%   $182.6718   $182.67   $182.65   $182.70  
  Purchase #7 $219.41   12.837%   $247.5757   $247.58   $247.60   $247.60  
  7 purchase totals = $1,120.98       $1,207.6032   $1,207.61   $1,207.65   $1,207.60