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 $170.68   13.669%   $194.0102   $194.01   $194.00   $194.00  
  Purchase #2 $247.25   9.868%   $271.6486   $271.65   $271.65   $271.60  
  Purchase #3 $95.90   11.459%   $106.8892   $106.89   $106.90   $106.90  
  Purchase #4 $16.76   12.382%   $18.8352   $18.84   $18.85   $18.80  
  Purchase #5 $163.92   4.528%   $171.3423   $171.34   $171.35   $171.30  
  Purchase #6 $62.36   9.666%   $68.3877   $68.39   $68.40   $68.40  
  Purchase #7 $192.55   6.270%   $204.6229   $204.62   $204.60   $204.60  
  7 purchase totals = $949.42       $1,035.7361   $1,035.74   $1,035.75   $1,035.60