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	$127.31	7.621%	$137.0123	$137.01	$137.00	$137.00
Purchase #2	$120.36	8.413%	$130.4859	$130.49	$130.50	$130.50
Purchase #3	$206.32	7.563%	$221.924	$221.92	$221.90	$221.90
Purchase #4	$97.72	11.681%	$109.1347	$109.13	$109.15	$109.10
Purchase #5	$99.31	13.130%	$112.3494	$112.35	$112.35	$112.30
Purchase #6	$91.89	12.244%	$103.141	$103.14	$103.15	$103.10
Purchase #7	$141.68	8.499%	$153.7214	$153.72	$153.70	$153.70
7 purchase totals =	$884.59		$967.7687	$967.76	$967.75	$967.60