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	$228.86	7.257%	$245.4684	$245.47	$245.45	$245.50
Purchase #2	$65.67	9.113%	$71.6545	$71.65	$71.65	$71.70
Purchase #3	$129.82	5.796%	$137.3444	$137.34	$137.35	$137.30
Purchase #4	$19.79	3.181%	$20.4195	$20.42	$20.40	$20.40
Purchase #5	$89.66	6.502%	$95.4897	$95.49	$95.50	$95.50
Purchase #6	$9.39	9.362%	$10.2691	$10.27	$10.25	$10.30
Purchase #7	$169.89	4.832%	$178.0991	$178.10	$178.10	$178.10
7 purchase totals =	$713.08		$758.7447	$758.74	$758.70	$758.80