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 $59.82   3.794%   $62.0896   $62.09   $62.10   $62.10  
  Purchase #2 $16.48   9.234%   $18.0018   $18.00   $18.00   $18.00  
  Purchase #3 $150.85   4.712%   $157.9581   $157.96   $157.95   $158.00  
  Purchase #4 $247.51   13.815%   $281.7035   $281.70   $281.70   $281.70  
  Purchase #5 $153.34   5.686%   $162.0589   $162.06   $162.05   $162.10  
  Purchase #6 $244.83   3.489%   $253.3721   $253.37   $253.35   $253.40  
  Purchase #7 $194.74   12.212%   $218.5216   $218.52   $218.50   $218.50  
  7 purchase totals = $1,067.57       $1,153.7056   $1,153.70   $1,153.65   $1,153.80