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 $64.98   7.532%   $69.8743   $69.87   $69.85   $69.90  
  Purchase #2 $143.94   6.775%   $153.6919   $153.69   $153.70   $153.70  
  Purchase #3 $227.51   5.376%   $239.7409   $239.74   $239.75   $239.70  
  Purchase #4 $113.73   3.638%   $117.8675   $117.87   $117.85   $117.90  
  Purchase #5 $171.96   8.536%   $186.6385   $186.64   $186.65   $186.60  
  Purchase #6 $91.67   6.562%   $97.6854   $97.69   $97.70   $97.70  
  Purchase #7 $160.30   5.434%   $169.0107   $169.01   $169.00   $169.00  
  7 purchase totals = $974.09       $1,034.5092   $1,034.51   $1,034.50   $1,034.50