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 $170.66   3.115%   $175.9761   $175.98   $176.00   $176.00  
  Purchase #2 $240.44   10.566%   $265.8449   $265.84   $265.85   $265.80  
  Purchase #3 $72.55   4.146%   $75.5579   $75.56   $75.55   $75.60  
  Purchase #4 $153.84   4.126%   $160.1874   $160.19   $160.20   $160.20  
  Purchase #5 $237.66   3.434%   $245.8212   $245.82   $245.80   $245.80  
  Purchase #6 $88.47   7.305%   $94.9327   $94.93   $94.95   $94.90  
  Purchase #7 $205.66   5.340%   $216.6422   $216.64   $216.65   $216.60  
  7 purchase totals = $1,169.28       $1,234.9624   $1,234.96   $1,235.00   $1,234.90