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 $43.51   3.313%   $44.9515   $44.95   $44.95   $45.00  
  Purchase #2 $71.63   7.458%   $76.9722   $76.97   $76.95   $77.00  
  Purchase #3 $124.94   4.547%   $130.621   $130.62   $130.60   $130.60  
  Purchase #4 $24.97   10.683%   $27.6375   $27.64   $27.65   $27.60  
  Purchase #5 $153.38   12.354%   $172.3286   $172.33   $172.35   $172.30  
  Purchase #6 $123.91   5.415%   $130.6197   $130.62   $130.60   $130.60  
  Purchase #7 $160.42   5.303%   $168.9271   $168.93   $168.95   $168.90  
  7 purchase totals = $702.76       $752.0576   $752.06   $752.05   $752.00