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	$226.41	3.688%	$234.76	$234.76	$234.75	$234.80
Purchase #2	$180.50	10.575%	$199.5879	$199.59	$199.60	$199.60
Purchase #3	$207.30	6.810%	$221.4171	$221.42	$221.40	$221.40
Purchase #4	$111.38	4.571%	$116.4712	$116.47	$116.45	$116.50
Purchase #5	$223.78	9.235%	$244.4461	$244.45	$244.45	$244.40
Purchase #6	$21.42	5.179%	$22.5293	$22.53	$22.55	$22.50
Purchase #7	$30.83	7.709%	$33.2067	$33.21	$33.20	$33.20
7 purchase totals =	$1,001.62		$1,072.4183	$1,072.43	$1,072.40	$1,072.40