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 $174.54   7.484%   $187.6026   $187.60   $187.60   $187.60  
  Purchase #2 $83.75   9.309%   $91.5463   $91.55   $91.55   $91.50  
  Purchase #3 $113.77   12.802%   $128.3348   $128.33   $128.35   $128.30  
  Purchase #4 $135.25   7.440%   $145.3126   $145.31   $145.30   $145.30  
  Purchase #5 $64.93   10.816%   $71.9528   $71.95   $71.95   $72.00  
  Purchase #6 $124.25   9.359%   $135.8786   $135.88   $135.90   $135.90  
  Purchase #7 $235.53   7.625%   $253.4892   $253.49   $253.50   $253.50  
  7 purchase totals = $932.02       $1,014.1169   $1,014.11   $1,014.15   $1,014.10