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 $109.51   4.257%   $114.1718   $114.17   $114.15   $114.20  
  Purchase #2 $210.94   4.126%   $219.6434   $219.64   $219.65   $219.60  
  Purchase #3 $148.64   4.356%   $155.1148   $155.11   $155.10   $155.10  
  Purchase #4 $212.94   12.621%   $239.8152   $239.82   $239.80   $239.80  
  Purchase #5 $203.29   3.772%   $210.9581   $210.96   $210.95   $211.00  
  Purchase #6 $185.45   13.224%   $209.9739   $209.97   $209.95   $210.00  
  Purchase #7 $50.55   4.763%   $52.9577   $52.96   $52.95   $53.00  
  7 purchase totals = $1,121.32       $1,202.6349   $1,202.63   $1,202.55   $1,202.70