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	$149.45	3.604%	$154.8362	$154.84	$154.85	$154.80
Purchase #2	$240.95	6.458%	$256.5106	$256.51	$256.50	$256.50
Purchase #3	$130.31	9.222%	$142.3272	$142.33	$142.35	$142.30
Purchase #4	$19.41	4.518%	$20.2869	$20.29	$20.30	$20.30
Purchase #5	$115.29	8.647%	$125.2591	$125.26	$125.25	$125.30
Purchase #6	$211.78	6.385%	$225.3022	$225.30	$225.30	$225.30
Purchase #7	$39.87	6.673%	$42.5305	$42.53	$42.55	$42.50
7 purchase totals =	$907.06		$967.0527	$967.06	$967.10	$967.00