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 $111.83   13.286%   $126.6877   $126.69   $126.70   $126.70  
  Purchase #2 $205.99   6.602%   $219.5895   $219.59   $219.60   $219.60  
  Purchase #3 $94.85   4.574%   $99.1884   $99.19   $99.20   $99.20  
  Purchase #4 $177.80   11.201%   $197.7154   $197.72   $197.70   $197.70  
  Purchase #5 $46.34   8.548%   $50.3011   $50.30   $50.30   $50.30  
  Purchase #6 $199.26   6.449%   $212.1103   $212.11   $212.10   $212.10  
  Purchase #7 $194.27   8.394%   $210.577   $210.58   $210.60   $210.60  
  7 purchase totals = $1,030.34       $1,116.1694   $1,116.18   $1,116.20   $1,116.20