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	$176.82	12.447%	$198.8288	$198.83	$198.85	$198.80
Purchase #2	$167.39	3.817%	$173.7793	$173.78	$173.80	$173.80
Purchase #3	$147.74	12.628%	$166.3966	$166.40	$166.40	$166.40
Purchase #4	$205.76	9.668%	$225.6529	$225.65	$225.65	$225.70
Purchase #5	$123.73	10.500%	$136.7217	$136.72	$136.70	$136.70
Purchase #6	$165.28	5.817%	$174.8943	$174.89	$174.90	$174.90
Purchase #7	$213.37	11.717%	$238.3706	$238.37	$238.35	$238.40
7 purchase totals =	$1,200.09		$1,314.6442	$1,314.64	$1,314.65	$1,314.70