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 $47.90   8.567%   $52.0036   $52.00   $52.00   $52.00  
  Purchase #2 $124.96   5.683%   $132.0615   $132.06   $132.05   $132.10  
  Purchase #3 $100.35   13.185%   $113.5811   $113.58   $113.60   $113.60  
  Purchase #4 $206.30   9.541%   $225.9831   $225.98   $226.00   $226.00  
  Purchase #5 $222.26   9.251%   $242.8213   $242.82   $242.80   $242.80  
  Purchase #6 $80.96   8.171%   $87.5752   $87.58   $87.60   $87.60  
  Purchase #7 $90.41   11.839%   $101.1136   $101.11   $101.10   $101.10  
  7 purchase totals = $873.14       $955.1394   $955.13   $955.15   $955.20