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 $23.57   4.183%   $24.5559   $24.56   $24.55   $24.60  
  Purchase #2 $214.99   12.699%   $242.2916   $242.29   $242.30   $242.30  
  Purchase #3 $60.26   11.460%   $67.1658   $67.17   $67.15   $67.20  
  Purchase #4 $187.29   13.802%   $213.1398   $213.14   $213.15   $213.10  
  Purchase #5 $217.52   10.435%   $240.2182   $240.22   $240.20   $240.20  
  Purchase #6 $215.40   10.591%   $238.213   $238.21   $238.20   $238.20  
  Purchase #7 $33.31   11.319%   $37.0804   $37.08   $37.10   $37.10  
  7 purchase totals = $952.34       $1,062.6647   $1,062.67   $1,062.65   $1,062.70