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 $171.43   7.361%   $184.049   $184.05   $184.05   $184.00  
  Purchase #2 $241.48   4.820%   $253.1193   $253.12   $253.10   $253.10  
  Purchase #3 $40.97   7.630%   $44.096   $44.10   $44.10   $44.10  
  Purchase #4 $110.64   12.874%   $124.8838   $124.88   $124.90   $124.90  
  Purchase #5 $165.92   4.133%   $172.7775   $172.78   $172.80   $172.80  
  Purchase #6 $206.84   7.103%   $221.5318   $221.53   $221.55   $221.50  
  Purchase #7 $32.46   7.709%   $34.9623   $34.96   $34.95   $35.00  
  7 purchase totals = $969.74       $1,035.4197   $1,035.42   $1,035.45   $1,035.40