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 $119.75   11.610%   $133.653   $133.65   $133.65   $133.70  
  Purchase #2 $235.52   10.550%   $260.3674   $260.37   $260.35   $260.40  
  Purchase #3 $176.85   11.526%   $197.2337   $197.23   $197.25   $197.20  
  Purchase #4 $85.44   10.814%   $94.6795   $94.68   $94.70   $94.70  
  Purchase #5 $50.68   6.303%   $53.8744   $53.87   $53.85   $53.90  
  Purchase #6 $65.97   11.850%   $73.7874   $73.79   $73.80   $73.80  
  Purchase #7 $234.91   5.498%   $247.8254   $247.83   $247.85   $247.80  
  7 purchase totals = $969.12       $1,061.4208   $1,061.42   $1,061.45   $1,061.50