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 $214.89   4.706%   $225.0027   $225.00   $225.00   $225.00  
  Purchase #2 $5.70   11.349%   $6.3469   $6.35   $6.35   $6.30  
  Purchase #3 $165.73   12.634%   $186.6683   $186.67   $186.65   $186.70  
  Purchase #4 $43.57   7.717%   $46.9323   $46.93   $46.95   $46.90  
  Purchase #5 $197.97   5.722%   $209.2978   $209.30   $209.30   $209.30  
  Purchase #6 $112.33   8.544%   $121.9275   $121.93   $121.95   $121.90  
  Purchase #7 $128.71   6.321%   $136.8458   $136.85   $136.85   $136.80  
  7 purchase totals = $868.90       $933.0213   $933.03   $933.05   $932.90