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	$153.50	10.444%	$169.5315	$169.53	$169.55	$169.50
Purchase #2	$236.83	4.388%	$247.2221	$247.22	$247.20	$247.20
Purchase #3	$33.56	5.203%	$35.3061	$35.31	$35.30	$35.30
Purchase #4	$44.62	13.671%	$50.72	$50.72	$50.70	$50.70
Purchase #5	$161.67	11.188%	$179.7576	$179.76	$179.75	$179.80
Purchase #6	$138.95	12.464%	$156.2687	$156.27	$156.25	$156.30
Purchase #7	$240.86	7.731%	$259.4809	$259.48	$259.50	$259.50
7 purchase totals =	$1,009.99		$1,098.2869	$1,098.29	$1,098.25	$1,098.30