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 $172.79   5.458%   $182.2209   $182.22   $182.20   $182.20  
  Purchase #2 $195.27   12.418%   $219.5186   $219.52   $219.50   $219.50  
  Purchase #3 $232.57   7.383%   $249.7406   $249.74   $249.75   $249.70  
  Purchase #4 $238.36   11.579%   $265.9597   $265.96   $265.95   $266.00  
  Purchase #5 $56.75   6.118%   $60.222   $60.22   $60.20   $60.20  
  Purchase #6 $118.69   5.335%   $125.0221   $125.02   $125.00   $125.00  
  Purchase #7 $188.40   7.751%   $203.0029   $203.00   $203.00   $203.00  
  7 purchase totals = $1,202.83       $1,305.6868   $1,305.68   $1,305.60   $1,305.60