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 $183.91   10.206%   $202.6799   $202.68   $202.70   $202.70  
  Purchase #2 $146.57   12.737%   $165.2386   $165.24   $165.25   $165.20  
  Purchase #3 $80.65   9.275%   $88.1303   $88.13   $88.15   $88.10  
  Purchase #4 $117.49   3.133%   $121.171   $121.17   $121.15   $121.20  
  Purchase #5 $185.68   5.228%   $195.3874   $195.39   $195.40   $195.40  
  Purchase #6 $155.70   10.341%   $171.8009   $171.80   $171.80   $171.80  
  Purchase #7 $203.26   3.359%   $210.0875   $210.09   $210.10   $210.10  
  7 purchase totals = $1,073.26       $1,154.4956   $1,154.50   $1,154.55   $1,154.50