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 $202.78   6.814%   $216.5974   $216.60   $216.60   $216.60  
  Purchase #2 $33.97   9.474%   $37.1883   $37.19   $37.20   $37.20  
  Purchase #3 $49.48   9.159%   $54.0119   $54.01   $54.00   $54.00  
  Purchase #4 $60.70   6.276%   $64.5095   $64.51   $64.50   $64.50  
  Purchase #5 $51.37   5.364%   $54.1255   $54.13   $54.15   $54.10  
  Purchase #6 $225.30   3.304%   $232.7439   $232.74   $232.75   $232.70  
  Purchase #7 $82.46   7.336%   $88.5093   $88.51   $88.50   $88.50  
  7 purchase totals = $706.06       $747.6858   $747.69   $747.70   $747.60