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	$60.66	11.322%	$67.5279	$67.53	$67.55	$67.50
Purchase #2	$50.32	4.614%	$52.6418	$52.64	$52.65	$52.60
Purchase #3	$33.67	4.504%	$35.1865	$35.19	$35.20	$35.20
Purchase #4	$71.38	11.228%	$79.3945	$79.39	$79.40	$79.40
Purchase #5	$196.90	4.590%	$205.9377	$205.94	$205.95	$205.90
Purchase #6	$241.77	3.601%	$250.4761	$250.48	$250.50	$250.50
Purchase #7	$97.37	8.759%	$105.8986	$105.90	$105.90	$105.90
7 purchase totals =	$752.07		$797.0631	$797.07	$797.15	$797.00