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 $213.60   10.336%   $235.6777   $235.68   $235.70   $235.70  
  Purchase #2 $158.46   12.258%   $177.884   $177.88   $177.90   $177.90  
  Purchase #3 $75.62   3.169%   $78.0164   $78.02   $78.00   $78.00  
  Purchase #4 $53.68   13.257%   $60.7964   $60.80   $60.80   $60.80  
  Purchase #5 $52.29   6.305%   $55.5869   $55.59   $55.60   $55.60  
  Purchase #6 $241.32   13.640%   $274.236   $274.24   $274.25   $274.20  
  Purchase #7 $136.56   12.117%   $153.107   $153.11   $153.10   $153.10  
  7 purchase totals = $931.53       $1,035.3044   $1,035.32   $1,035.35   $1,035.30