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 $72.41   4.381%   $75.5823   $75.58   $75.60   $75.60  
  Purchase #2 $228.43   8.293%   $247.3737   $247.37   $247.35   $247.40  
  Purchase #3 $95.87   6.714%   $102.3067   $102.31   $102.30   $102.30  
  Purchase #4 $247.87   9.489%   $271.3904   $271.39   $271.40   $271.40  
  Purchase #5 $89.51   8.666%   $97.2669   $97.27   $97.25   $97.30  
  Purchase #6 $87.60   7.823%   $94.4529   $94.45   $94.45   $94.50  
  Purchase #7 $157.42   10.673%   $174.2214   $174.22   $174.20   $174.20  
  7 purchase totals = $979.11       $1,062.5943   $1,062.59   $1,062.55   $1,062.70