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	$166.49	7.603%	$179.1482	$179.15	$179.15	$179.10
Purchase #2	$200.39	3.834%	$208.073	$208.07	$208.05	$208.10
Purchase #3	$42.68	7.410%	$45.8426	$45.84	$45.85	$45.80
Purchase #4	$78.89	6.781%	$84.2395	$84.24	$84.25	$84.20
Purchase #5	$150.89	5.728%	$159.533	$159.53	$159.55	$159.50
Purchase #6	$215.65	13.857%	$245.5326	$245.53	$245.55	$245.50
Purchase #7	$17.72	10.171%	$19.5223	$19.52	$19.50	$19.50
7 purchase totals =	$872.71		$941.8912	$941.88	$941.90	$941.70