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 $104.89   8.207%   $113.4983   $113.50   $113.50   $113.50  
  Purchase #2 $111.88   4.263%   $116.6494   $116.65   $116.65   $116.60  
  Purchase #3 $172.29   12.575%   $193.9555   $193.96   $193.95   $194.00  
  Purchase #4 $117.74   6.132%   $124.9598   $124.96   $124.95   $125.00  
  Purchase #5 $166.52   11.825%   $186.211   $186.21   $186.20   $186.20  
  Purchase #6 $106.30   3.349%   $109.86   $109.86   $109.85   $109.90  
  Purchase #7 $168.57   13.443%   $191.2309   $191.23   $191.25   $191.20  
  7 purchase totals = $948.19       $1,036.3649   $1,036.37   $1,036.35   $1,036.40