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 $84.64   11.573%   $94.4354   $94.44   $94.45   $94.40  
  Purchase #2 $181.52   11.534%   $202.4565   $202.46   $202.45   $202.50  
  Purchase #3 $213.75   7.320%   $229.3965   $229.40   $229.40   $229.40  
  Purchase #4 $34.84   4.119%   $36.2751   $36.28   $36.30   $36.30  
  Purchase #5 $17.68   5.414%   $18.6372   $18.64   $18.65   $18.60  
  Purchase #6 $125.58   12.465%   $141.2335   $141.23   $141.25   $141.20  
  Purchase #7 $246.44   10.355%   $271.9589   $271.96   $271.95   $272.00  
  7 purchase totals = $904.45       $994.3931   $994.41   $994.45   $994.40