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	$243.87	10.481%	$269.43	$269.43	$269.45	$269.40
Purchase #2	$244.37	12.703%	$275.4123	$275.41	$275.40	$275.40
Purchase #3	$204.82	11.603%	$228.5853	$228.59	$228.60	$228.60
Purchase #4	$98.57	12.114%	$110.5108	$110.51	$110.50	$110.50
Purchase #5	$22.32	5.147%	$23.4688	$23.47	$23.45	$23.50
Purchase #6	$105.50	6.616%	$112.4799	$112.48	$112.50	$112.50
Purchase #7	$9.47	12.163%	$10.6218	$10.62	$10.60	$10.60
7 purchase totals =	$928.92		$1,030.5089	$1,030.51	$1,030.50	$1,030.50