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 $216.34   6.555%   $230.5211   $230.52   $230.50   $230.50  
  Purchase #2 $97.60   4.813%   $102.2975   $102.30   $102.30   $102.30  
  Purchase #3 $9.85   8.634%   $10.7004   $10.70   $10.70   $10.70  
  Purchase #4 $101.69   12.831%   $114.7378   $114.74   $114.75   $114.70  
  Purchase #5 $244.94   10.156%   $269.8161   $269.82   $269.80   $269.80  
  Purchase #6 $94.97   5.864%   $100.539   $100.54   $100.55   $100.50  
  Purchase #7 $161.95   3.106%   $166.9802   $166.98   $167.00   $167.00  
  7 purchase totals = $927.34       $995.5921   $995.60   $995.60   $995.50