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	$97.40	3.847%	$101.147	$101.15	$101.15	$101.10
Purchase #2	$181.31	8.200%	$196.1774	$196.18	$196.20	$196.20
Purchase #3	$61.66	6.304%	$65.547	$65.55	$65.55	$65.50
Purchase #4	$58.58	6.675%	$62.4902	$62.49	$62.50	$62.50
Purchase #5	$73.59	4.667%	$77.0244	$77.02	$77.00	$77.00
Purchase #6	$52.93	12.447%	$59.5182	$59.52	$59.50	$59.50
Purchase #7	$148.28	9.763%	$162.7566	$162.76	$162.75	$162.80
7 purchase totals =	$673.75		$724.6608	$724.67	$724.65	$724.60