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 $72.93   4.159%   $75.9632   $75.96   $75.95   $76.00  
  Purchase #2 $223.26   13.546%   $253.5028   $253.50   $253.50   $253.50  
  Purchase #3 $217.71   6.187%   $231.1797   $231.18   $231.20   $231.20  
  Purchase #4 $73.47   8.401%   $79.6422   $79.64   $79.65   $79.60  
  Purchase #5 $153.68   5.362%   $161.9203   $161.92   $161.90   $161.90  
  Purchase #6 $187.33   8.556%   $203.358   $203.36   $203.35   $203.40  
  Purchase #7 $145.28   6.332%   $154.4791   $154.48   $154.50   $154.50  
  7 purchase totals = $1,073.66       $1,160.0453   $1,160.04   $1,160.05   $1,160.10