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 $46.76   12.753%   $52.7233   $52.72   $52.70   $52.70  
  Purchase #2 $140.84   8.747%   $153.1593   $153.16   $153.15   $153.20  
  Purchase #3 $170.98   12.343%   $192.0841   $192.08   $192.10   $192.10  
  Purchase #4 $208.57   4.234%   $217.4009   $217.40   $217.40   $217.40  
  Purchase #5 $86.73   9.518%   $94.985   $94.99   $95.00   $95.00  
  Purchase #6 $169.49   10.443%   $187.1898   $187.19   $187.20   $187.20  
  Purchase #7 $230.29   10.753%   $255.0531   $255.05   $255.05   $255.10  
  7 purchase totals = $1,053.66       $1,152.5955   $1,152.59   $1,152.60   $1,152.70