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 $134.90   7.562%   $145.1011   $145.10   $145.10   $145.10  
  Purchase #2 $62.38   11.512%   $69.5612   $69.56   $69.55   $69.60  
  Purchase #3 $22.90   8.402%   $24.8241   $24.82   $24.80   $24.80  
  Purchase #4 $213.29   5.381%   $224.7671   $224.77   $224.75   $224.80  
  Purchase #5 $228.66   9.293%   $249.9094   $249.91   $249.90   $249.90  
  Purchase #6 $36.54   8.794%   $39.7533   $39.75   $39.75   $39.80  
  Purchase #7 $99.91   10.109%   $110.0099   $110.01   $110.00   $110.00  
  7 purchase totals = $798.58       $863.9261   $863.92   $863.85   $864.00