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	$99.38	6.105%	$105.4471	$105.45	$105.45	$105.40
Purchase #2	$125.66	3.551%	$130.1222	$130.12	$130.10	$130.10
Purchase #3	$112.33	5.507%	$118.516	$118.52	$118.50	$118.50
Purchase #4	$92.74	13.345%	$105.1162	$105.12	$105.10	$105.10
Purchase #5	$12.73	3.509%	$13.1767	$13.18	$13.20	$13.20
Purchase #6	$166.52	11.556%	$185.7631	$185.76	$185.75	$185.80
Purchase #7	$64.68	13.751%	$73.5741	$73.57	$73.55	$73.60
7 purchase totals =	$674.04		$731.7154	$731.72	$731.65	$731.70