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 $191.59   5.596%   $202.3114   $202.31   $202.30   $202.30  
  Purchase #2 $62.42   13.186%   $70.6507   $70.65   $70.65   $70.70  
  Purchase #3 $111.43   6.362%   $118.5192   $118.52   $118.50   $118.50  
  Purchase #4 $200.91   10.823%   $222.6545   $222.65   $222.65   $222.70  
  Purchase #5 $170.40   7.838%   $183.756   $183.76   $183.75   $183.80  
  Purchase #6 $171.47   9.257%   $187.343   $187.34   $187.35   $187.30  
  Purchase #7 $170.72   7.110%   $182.8582   $182.86   $182.85   $182.90  
  7 purchase totals = $1,078.94       $1,168.0930   $1,168.09   $1,168.05   $1,168.20