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 $62.36   9.147%   $68.0641   $68.06   $68.05   $68.10  
  Purchase #2 $160.77   4.753%   $168.4114   $168.41   $168.40   $168.40  
  Purchase #3 $230.63   6.819%   $246.3567   $246.36   $246.35   $246.40  
  Purchase #4 $118.82   9.327%   $129.9023   $129.90   $129.90   $129.90  
  Purchase #5 $46.32   5.849%   $49.0293   $49.03   $49.05   $49.00  
  Purchase #6 $132.66   11.289%   $147.636   $147.64   $147.65   $147.60  
  Purchase #7 $216.90   10.785%   $240.2927   $240.29   $240.30   $240.30  
  7 purchase totals = $968.46       $1,049.6925   $1,049.69   $1,049.70   $1,049.70