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	$72.27	3.182%	$74.5696	$74.57	$74.55	$74.60
Purchase #2	$69.59	12.456%	$78.2581	$78.26	$78.25	$78.30
Purchase #3	$148.84	9.130%	$162.4291	$162.43	$162.45	$162.40
Purchase #4	$102.37	13.614%	$116.3067	$116.31	$116.30	$116.30
Purchase #5	$53.71	12.698%	$60.5301	$60.53	$60.55	$60.50
Purchase #6	$179.52	4.796%	$188.1298	$188.13	$188.15	$188.10
Purchase #7	$18.40	13.651%	$20.9118	$20.91	$20.90	$20.90
7 purchase totals =	$644.70		$701.1352	$701.14	$701.15	$701.10