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 $69.26   11.626%   $77.3122   $77.31   $77.30   $77.30  
  Purchase #2 $197.61   7.660%   $212.7469   $212.75   $212.75   $212.70  
  Purchase #3 $194.64   11.225%   $216.4883   $216.49   $216.50   $216.50  
  Purchase #4 $88.81   3.338%   $91.7745   $91.77   $91.75   $91.80  
  Purchase #5 $66.72   11.432%   $74.3474   $74.35   $74.35   $74.30  
  Purchase #6 $60.33   5.200%   $63.4672   $63.47   $63.45   $63.50  
  Purchase #7 $109.89   7.667%   $118.3153   $118.32   $118.30   $118.30  
  7 purchase totals = $787.26       $854.4518   $854.46   $854.40   $854.40