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	$32.94	8.113%	$35.6124	$35.61	$35.60	$35.60
Purchase #2	$161.97	10.841%	$179.5292	$179.53	$179.55	$179.50
Purchase #3	$50.46	5.786%	$53.3796	$53.38	$53.40	$53.40
Purchase #4	$154.84	3.707%	$160.5799	$160.58	$160.60	$160.60
Purchase #5	$40.40	5.581%	$42.6547	$42.65	$42.65	$42.70
Purchase #6	$164.74	6.816%	$175.9687	$175.97	$175.95	$176.00
Purchase #7	$247.63	3.247%	$255.6705	$255.67	$255.65	$255.70
7 purchase totals =	$852.98		$903.3950	$903.39	$903.40	$903.50