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	$189.81	4.674%	$198.6817	$198.68	$198.70	$198.70
Purchase #2	$187.96	7.429%	$201.9235	$201.92	$201.90	$201.90
Purchase #3	$93.46	7.117%	$100.1115	$100.11	$100.10	$100.10
Purchase #4	$247.31	3.301%	$255.4737	$255.47	$255.45	$255.50
Purchase #5	$37.71	13.347%	$42.7432	$42.74	$42.75	$42.70
Purchase #6	$164.61	5.679%	$173.9582	$173.96	$173.95	$174.00
Purchase #7	$10.62	7.626%	$11.4299	$11.43	$11.45	$11.40
7 purchase totals =	$931.48		$984.3217	$984.31	$984.30	$984.30