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	$165.59	13.103%	$187.2873	$187.29	$187.30	$187.30
Purchase #2	$33.49	7.281%	$35.9284	$35.93	$35.95	$35.90
Purchase #3	$77.95	6.613%	$83.1048	$83.10	$83.10	$83.10
Purchase #4	$62.81	7.562%	$67.5597	$67.56	$67.55	$67.60
Purchase #5	$53.58	4.614%	$56.0522	$56.05	$56.05	$56.10
Purchase #6	$154.65	7.660%	$166.4962	$166.50	$166.50	$166.50
Purchase #7	$134.66	5.477%	$142.0353	$142.04	$142.05	$142.00
7 purchase totals =	$682.73		$738.4639	$738.47	$738.50	$738.50