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 $196.35   7.608%   $211.2883   $211.29   $211.30   $211.30  
  Purchase #2 $233.39   3.337%   $241.1782   $241.18   $241.20   $241.20  
  Purchase #3 $20.95   4.698%   $21.9342   $21.93   $21.95   $21.90  
  Purchase #4 $52.67   13.417%   $59.7367   $59.74   $59.75   $59.70  
  Purchase #5 $181.26   3.224%   $187.1038   $187.10   $187.10   $187.10  
  Purchase #6 $16.72   9.485%   $18.3059   $18.31   $18.30   $18.30  
  Purchase #7 $202.97   3.740%   $210.5611   $210.56   $210.55   $210.60  
  7 purchase totals = $904.31       $950.1082   $950.11   $950.15   $950.10