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	$181.78	5.141%	$191.1253	$191.13	$191.15	$191.10
Purchase #2	$112.31	12.647%	$126.5138	$126.51	$126.50	$126.50
Purchase #3	$158.64	12.164%	$177.937	$177.94	$177.95	$177.90
Purchase #4	$247.91	10.834%	$274.7686	$274.77	$274.75	$274.80
Purchase #5	$178.60	10.243%	$196.894	$196.89	$196.90	$196.90
Purchase #6	$57.81	13.827%	$65.8034	$65.80	$65.80	$65.80
Purchase #7	$248.83	8.355%	$269.6197	$269.62	$269.60	$269.60
7 purchase totals =	$1,185.88		$1,302.6618	$1,302.66	$1,302.65	$1,302.60