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	$22.46	12.500%	$25.2675	$25.27	$25.25	$25.30
Purchase #2	$119.34	7.576%	$128.3812	$128.38	$128.40	$128.40
Purchase #3	$145.95	13.486%	$165.6328	$165.63	$165.65	$165.60
Purchase #4	$148.70	4.287%	$155.0748	$155.07	$155.05	$155.10
Purchase #5	$22.49	13.603%	$25.5493	$25.55	$25.55	$25.50
Purchase #6	$170.81	4.784%	$178.9816	$178.98	$179.00	$179.00
Purchase #7	$196.52	13.185%	$222.4312	$222.43	$222.45	$222.40
7 purchase totals =	$826.27		$901.3184	$901.31	$901.35	$901.30