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 $219.27   6.700%   $233.9611   $233.96   $233.95   $234.00  
  Purchase #2 $246.84   11.644%   $275.582   $275.58   $275.60   $275.60  
  Purchase #3 $213.74   7.605%   $229.9949   $229.99   $230.00   $230.00  
  Purchase #4 $180.44   9.632%   $197.82   $197.82   $197.80   $197.80  
  Purchase #5 $217.95   12.293%   $244.7426   $244.74   $244.75   $244.70  
  Purchase #6 $101.67   7.687%   $109.4854   $109.49   $109.50   $109.50  
  Purchase #7 $114.47   3.590%   $118.5795   $118.58   $118.60   $118.60  
  7 purchase totals = $1,294.38       $1,410.1655   $1,410.16   $1,410.20   $1,410.20