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 $164.95   6.520%   $175.7047   $175.70   $175.70   $175.70  
  Purchase #2 $92.34   10.150%   $101.7125   $101.71   $101.70   $101.70  
  Purchase #3 $86.60   7.178%   $92.8161   $92.82   $92.80   $92.80  
  Purchase #4 $159.50   6.697%   $170.1817   $170.18   $170.20   $170.20  
  Purchase #5 $191.70   5.122%   $201.5189   $201.52   $201.50   $201.50  
  Purchase #6 $172.92   11.594%   $192.9683   $192.97   $192.95   $193.00  
  Purchase #7 $76.73   3.604%   $79.4953   $79.50   $79.50   $79.50  
  7 purchase totals = $944.74       $1,014.3975   $1,014.40   $1,014.35   $1,014.40