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	$129.79	3.677%	$134.5624	$134.56	$134.55	$134.60
Purchase #2	$55.61	9.500%	$60.893	$60.89	$60.90	$60.90
Purchase #3	$166.73	4.547%	$174.3112	$174.31	$174.30	$174.30
Purchase #4	$11.59	10.846%	$12.8471	$12.85	$12.85	$12.80
Purchase #5	$202.92	11.265%	$225.7789	$225.78	$225.80	$225.80
Purchase #6	$124.97	9.293%	$136.5835	$136.58	$136.60	$136.60
Purchase #7	$49.68	10.485%	$54.8889	$54.89	$54.90	$54.90
7 purchase totals =	$741.29		$799.8650	$799.86	$799.90	$799.90