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 $153.95   9.578%   $168.6953   $168.70   $168.70   $168.70  
  Purchase #2 $48.40   8.383%   $52.4574   $52.46   $52.45   $52.50  
  Purchase #3 $23.36   8.413%   $25.3253   $25.33   $25.35   $25.30  
  Purchase #4 $102.40   11.693%   $114.3736   $114.37   $114.35   $114.40  
  Purchase #5 $198.84   7.836%   $214.4211   $214.42   $214.40   $214.40  
  Purchase #6 $64.64   6.521%   $68.8552   $68.86   $68.85   $68.90  
  Purchase #7 $102.85   3.858%   $106.818   $106.82   $106.80   $106.80  
  7 purchase totals = $694.44       $750.9459   $750.96   $750.90   $751.00