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	$69.83	5.633%	$73.7635	$73.76	$73.75	$73.80
Purchase #2	$133.46	4.633%	$139.6432	$139.64	$139.65	$139.60
Purchase #3	$151.98	13.494%	$172.4882	$172.49	$172.50	$172.50
Purchase #4	$202.43	10.333%	$223.3471	$223.35	$223.35	$223.30
Purchase #5	$99.60	13.137%	$112.6845	$112.68	$112.70	$112.70
Purchase #6	$197.66	12.865%	$223.089	$223.09	$223.10	$223.10
Purchase #7	$86.45	4.193%	$90.0748	$90.07	$90.05	$90.10
7 purchase totals =	$941.41		$1,035.0903	$1,035.08	$1,035.10	$1,035.10