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	$159.72	3.141%	$164.7368	$164.74	$164.75	$164.70
Purchase #2	$153.34	12.869%	$173.0733	$173.07	$173.05	$173.10
Purchase #3	$154.85	13.230%	$175.3367	$175.34	$175.35	$175.30
Purchase #4	$40.69	3.325%	$42.0429	$42.04	$42.05	$42.00
Purchase #5	$190.54	8.414%	$206.572	$206.57	$206.55	$206.60
Purchase #6	$124.46	5.485%	$131.2866	$131.29	$131.30	$131.30
Purchase #7	$187.27	4.342%	$195.4013	$195.40	$195.40	$195.40
7 purchase totals =	$1,010.87		$1,088.4496	$1,088.45	$1,088.45	$1,088.40