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 $69.92   10.551%   $77.2973   $77.30   $77.30   $77.30  
  Purchase #2 $213.31   5.564%   $225.1786   $225.18   $225.20   $225.20  
  Purchase #3 $249.91   9.794%   $274.3862   $274.39   $274.40   $274.40  
  Purchase #4 $66.37   3.141%   $68.4547   $68.45   $68.45   $68.50  
  Purchase #5 $162.37   4.552%   $169.7611   $169.76   $169.75   $169.80  
  Purchase #6 $188.73   8.118%   $204.0511   $204.05   $204.05   $204.10  
  Purchase #7 $102.37   10.388%   $113.0042   $113.00   $113.00   $113.00  
  7 purchase totals = $1,052.98       $1,132.1332   $1,132.13   $1,132.15   $1,132.30