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	$66.48	8.493%	$72.1261	$72.13	$72.15	$72.10
Purchase #2	$53.53	11.163%	$59.5056	$59.51	$59.50	$59.50
Purchase #3	$111.38	5.306%	$117.2898	$117.29	$117.30	$117.30
Purchase #4	$228.79	11.249%	$254.5266	$254.53	$254.55	$254.50
Purchase #5	$70.86	8.519%	$76.8966	$76.90	$76.90	$76.90
Purchase #6	$240.36	4.867%	$252.0583	$252.06	$252.05	$252.10
Purchase #7	$239.56	11.164%	$266.3045	$266.30	$266.30	$266.30
7 purchase totals =	$1,010.96		$1,098.7075	$1,098.72	$1,098.75	$1,098.70