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	$233.50	5.449%	$246.2234	$246.22	$246.20	$246.20
Purchase #2	$152.86	4.517%	$159.7647	$159.76	$159.75	$159.80
Purchase #3	$124.40	5.143%	$130.7979	$130.80	$130.80	$130.80
Purchase #4	$165.87	7.366%	$178.088	$178.09	$178.10	$178.10
Purchase #5	$170.45	11.821%	$190.5989	$190.60	$190.60	$190.60
Purchase #6	$215.89	10.503%	$238.5649	$238.56	$238.55	$238.60
Purchase #7	$104.66	4.353%	$109.2158	$109.22	$109.20	$109.20
7 purchase totals =	$1,167.63		$1,253.2536	$1,253.25	$1,253.20	$1,253.30