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 $181.84   11.206%   $202.217   $202.22   $202.20   $202.20  
  Purchase #2 $62.44   3.198%   $64.4368   $64.44   $64.45   $64.40  
  Purchase #3 $230.33   13.499%   $261.4222   $261.42   $261.40   $261.40  
  Purchase #4 $63.93   6.302%   $67.9589   $67.96   $67.95   $68.00  
  Purchase #5 $96.91   11.868%   $108.4113   $108.41   $108.40   $108.40  
  Purchase #6 $129.40   10.505%   $142.9935   $142.99   $143.00   $143.00  
  Purchase #7 $207.40   4.203%   $216.117   $216.12   $216.10   $216.10  
  7 purchase totals = $972.25       $1,063.5567   $1,063.56   $1,063.50   $1,063.50