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	$172.81	13.318%	$195.8248	$195.82	$195.80	$195.80
Purchase #2	$11.98	9.596%	$13.1296	$13.13	$13.15	$13.10
Purchase #3	$106.81	7.294%	$114.6007	$114.60	$114.60	$114.60
Purchase #4	$244.67	12.698%	$275.7382	$275.74	$275.75	$275.70
Purchase #5	$75.72	3.459%	$78.3392	$78.34	$78.35	$78.30
Purchase #6	$52.51	7.720%	$56.5638	$56.56	$56.55	$56.60
Purchase #7	$234.69	10.721%	$259.8511	$259.85	$259.85	$259.90
7 purchase totals =	$899.19		$994.0474	$994.04	$994.05	$994.00