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 $213.96   11.217%   $237.9599   $237.96   $237.95   $238.00  
  Purchase #2 $220.46   3.575%   $228.3414   $228.34   $228.35   $228.30  
  Purchase #3 $59.41   12.381%   $66.7656   $66.77   $66.75   $66.80  
  Purchase #4 $227.33   12.814%   $256.4601   $256.46   $256.45   $256.50  
  Purchase #5 $121.95   5.643%   $128.8316   $128.83   $128.85   $128.80  
  Purchase #6 $66.99   7.843%   $72.244   $72.24   $72.25   $72.20  
  Purchase #7 $50.45   9.308%   $55.1459   $55.15   $55.15   $55.10  
  7 purchase totals = $960.55       $1,045.7485   $1,045.75   $1,045.75   $1,045.70