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 $211.84   9.611%   $232.1999   $232.20   $232.20   $232.20  
  Purchase #2 $240.89   9.758%   $264.396   $264.40   $264.40   $264.40  
  Purchase #3 $119.95   11.292%   $133.4948   $133.49   $133.50   $133.50  
  Purchase #4 $211.34   8.672%   $229.6674   $229.67   $229.65   $229.70  
  Purchase #5 $61.89   7.145%   $66.312   $66.31   $66.30   $66.30  
  Purchase #6 $91.46   6.550%   $97.4506   $97.45   $97.45   $97.50  
  Purchase #7 $125.96   5.815%   $133.2846   $133.28   $133.30   $133.30  
  7 purchase totals = $1,063.33       $1,156.8053   $1,156.80   $1,156.80   $1,156.90