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	$185.73	3.283%	$191.8275	$191.83	$191.85	$191.80
Purchase #2	$68.50	9.228%	$74.8212	$74.82	$74.80	$74.80
Purchase #3	$42.83	5.642%	$45.2465	$45.25	$45.25	$45.20
Purchase #4	$201.67	13.695%	$229.2887	$229.29	$229.30	$229.30
Purchase #5	$148.52	10.671%	$164.3686	$164.37	$164.35	$164.40
Purchase #6	$244.28	11.197%	$271.632	$271.63	$271.65	$271.60
Purchase #7	$205.64	7.696%	$221.4661	$221.47	$221.45	$221.50
7 purchase totals =	$1,097.17		$1,198.6506	$1,198.66	$1,198.65	$1,198.60