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	$108.56	10.315%	$119.758	$119.76	$119.75	$119.80
Purchase #2	$100.67	7.450%	$108.1699	$108.17	$108.15	$108.20
Purchase #3	$189.39	3.731%	$196.4561	$196.46	$196.45	$196.50
Purchase #4	$83.28	13.420%	$94.4562	$94.46	$94.45	$94.50
Purchase #5	$233.71	9.544%	$256.0153	$256.02	$256.00	$256.00
Purchase #6	$243.79	3.612%	$252.5957	$252.60	$252.60	$252.60
Purchase #7	$53.76	5.201%	$56.5561	$56.56	$56.55	$56.60
7 purchase totals =	$1,013.16		$1,084.0073	$1,084.03	$1,083.95	$1,084.20