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 $73.86   4.657%   $77.2997   $77.30   $77.30   $77.30  
  Purchase #2 $153.84   10.294%   $169.6763   $169.68   $169.70   $169.70  
  Purchase #3 $107.58   4.321%   $112.2285   $112.23   $112.25   $112.20  
  Purchase #4 $246.35   11.731%   $275.2493   $275.25   $275.25   $275.20  
  Purchase #5 $139.86   10.334%   $154.3131   $154.31   $154.30   $154.30  
  Purchase #6 $70.75   6.641%   $75.4485   $75.45   $75.45   $75.40  
  Purchase #7 $229.39   4.314%   $239.2859   $239.29   $239.30   $239.30  
  7 purchase totals = $1,021.63       $1,103.5013   $1,103.51   $1,103.55   $1,103.40