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 $211.32   4.717%   $221.288   $221.29   $221.30   $221.30  
  Purchase #2 $39.59   4.394%   $41.3296   $41.33   $41.35   $41.30  
  Purchase #3 $191.96   6.566%   $204.5641   $204.56   $204.55   $204.60  
  Purchase #4 $250.52   5.206%   $263.5621   $263.56   $263.55   $263.60  
  Purchase #5 $175.99   5.473%   $185.6219   $185.62   $185.60   $185.60  
  Purchase #6 $101.59   5.619%   $107.2983   $107.30   $107.30   $107.30  
  Purchase #7 $195.99   3.433%   $202.7183   $202.72   $202.70   $202.70  
  7 purchase totals = $1,166.96       $1,226.3823   $1,226.38   $1,226.35   $1,226.40