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	$158.95	12.257%	$178.4325	$178.43	$178.45	$178.40
Purchase #2	$39.58	11.783%	$44.2437	$44.24	$44.25	$44.20
Purchase #3	$233.72	4.361%	$243.9125	$243.91	$243.90	$243.90
Purchase #4	$91.62	8.244%	$99.1732	$99.17	$99.15	$99.20
Purchase #5	$35.74	13.118%	$40.4284	$40.43	$40.45	$40.40
Purchase #6	$126.52	5.232%	$133.1395	$133.14	$133.15	$133.10
Purchase #7	$242.83	13.577%	$275.799	$275.80	$275.80	$275.80
7 purchase totals =	$928.96		$1,015.1288	$1,015.12	$1,015.15	$1,015.00