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 $41.43   6.180%   $43.9904   $43.99   $44.00   $44.00  
  Purchase #2 $231.96   5.148%   $243.9013   $243.90   $243.90   $243.90  
  Purchase #3 $92.64   4.293%   $96.617   $96.62   $96.60   $96.60  
  Purchase #4 $183.55   11.250%   $204.1994   $204.20   $204.20   $204.20  
  Purchase #5 $66.69   6.690%   $71.1516   $71.15   $71.15   $71.20  
  Purchase #6 $152.53   6.546%   $162.5146   $162.51   $162.50   $162.50  
  Purchase #7 $101.64   6.865%   $108.6176   $108.62   $108.60   $108.60  
  7 purchase totals = $870.44       $930.9919   $930.99   $930.95   $931.00