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 $88.58   6.258%   $94.1233   $94.12   $94.10   $94.10  
  Purchase #2 $105.84   5.153%   $111.2939   $111.29   $111.30   $111.30  
  Purchase #3 $223.43   5.252%   $235.1645   $235.16   $235.15   $235.20  
  Purchase #4 $97.27   13.276%   $110.1836   $110.18   $110.20   $110.20  
  Purchase #5 $181.29   4.297%   $189.08   $189.08   $189.10   $189.10  
  Purchase #6 $249.57   5.692%   $263.7755   $263.78   $263.80   $263.80  
  Purchase #7 $207.67   3.797%   $215.5552   $215.56   $215.55   $215.60  
  7 purchase totals = $1,153.65       $1,219.1760   $1,219.17   $1,219.20   $1,219.30