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 $53.85   13.320%   $61.0228   $61.02   $61.00   $61.00  
  Purchase #2 $149.35   5.283%   $157.2402   $157.24   $157.25   $157.20  
  Purchase #3 $159.35   12.133%   $178.6839   $178.68   $178.70   $178.70  
  Purchase #4 $52.25   12.415%   $58.7368   $58.74   $58.75   $58.70  
  Purchase #5 $202.66   11.826%   $226.6266   $226.63   $226.65   $226.60  
  Purchase #6 $169.55   12.308%   $190.4182   $190.42   $190.40   $190.40  
  Purchase #7 $172.93   10.589%   $191.2416   $191.24   $191.25   $191.20  
  7 purchase totals = $959.94       $1,063.9701   $1,063.97   $1,064.00   $1,063.80