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 $145.90   4.818%   $152.9295   $152.93   $152.95   $152.90  
  Purchase #2 $176.57   10.396%   $194.9262   $194.93   $194.95   $194.90  
  Purchase #3 $43.71   13.597%   $49.6532   $49.65   $49.65   $49.70  
  Purchase #4 $166.29   4.189%   $173.2559   $173.26   $173.25   $173.30  
  Purchase #5 $218.59   11.677%   $244.1148   $244.11   $244.10   $244.10  
  Purchase #6 $198.45   13.842%   $225.9194   $225.92   $225.90   $225.90  
  Purchase #7 $20.33   11.594%   $22.6871   $22.69   $22.70   $22.70  
  7 purchase totals = $969.84       $1,063.4861   $1,063.49   $1,063.50   $1,063.50