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 $217.95   7.575%   $234.4597   $234.46   $234.45   $234.50  
  Purchase #2 $194.96   4.829%   $204.3746   $204.37   $204.35   $204.40  
  Purchase #3 $248.91   8.109%   $269.0941   $269.09   $269.10   $269.10  
  Purchase #4 $168.94   3.169%   $174.2937   $174.29   $174.30   $174.30  
  Purchase #5 $158.74   8.550%   $172.3123   $172.31   $172.30   $172.30  
  Purchase #6 $118.73   7.723%   $127.8995   $127.90   $127.90   $127.90  
  Purchase #7 $80.75   4.148%   $84.0995   $84.10   $84.10   $84.10  
  7 purchase totals = $1,188.98       $1,266.5334   $1,266.52   $1,266.50   $1,266.60