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	$171.84	3.243%	$177.4128	$177.41	$177.40	$177.40
Purchase #2	$92.66	8.364%	$100.4101	$100.41	$100.40	$100.40
Purchase #3	$108.76	6.180%	$115.4814	$115.48	$115.50	$115.50
Purchase #4	$246.47	7.175%	$264.1542	$264.15	$264.15	$264.20
Purchase #5	$158.28	6.272%	$168.2073	$168.21	$168.20	$168.20
Purchase #6	$37.96	9.634%	$41.6171	$41.62	$41.60	$41.60
Purchase #7	$133.70	13.525%	$151.7829	$151.78	$151.80	$151.80
7 purchase totals =	$949.67		$1,019.0658	$1,019.06	$1,019.05	$1,019.10