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	$39.91	11.512%	$44.5044	$44.50	$44.50	$44.50
Purchase #2	$198.39	7.224%	$212.7217	$212.72	$212.70	$212.70
Purchase #3	$59.73	9.313%	$65.2927	$65.29	$65.30	$65.30
Purchase #4	$145.32	6.448%	$154.6902	$154.69	$154.70	$154.70
Purchase #5	$69.76	5.126%	$73.3359	$73.34	$73.35	$73.30
Purchase #6	$83.61	7.329%	$89.7378	$89.74	$89.75	$89.70
Purchase #7	$115.83	10.175%	$127.6157	$127.62	$127.60	$127.60
7 purchase totals =	$712.55		$767.8984	$767.90	$767.90	$767.80