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 $61.68   10.461%   $68.1323   $68.13   $68.15   $68.10  
  Purchase #2 $205.69   5.322%   $216.6368   $216.64   $216.65   $216.60  
  Purchase #3 $203.46   13.193%   $230.3025   $230.30   $230.30   $230.30  
  Purchase #4 $138.95   6.504%   $147.9873   $147.99   $148.00   $148.00  
  Purchase #5 $161.68   13.672%   $183.7849   $183.78   $183.80   $183.80  
  Purchase #6 $169.41   8.677%   $184.1097   $184.11   $184.10   $184.10  
  Purchase #7 $109.42   4.445%   $114.2837   $114.28   $114.30   $114.30  
  7 purchase totals = $1,050.29       $1,145.2372   $1,145.23   $1,145.30   $1,145.20