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	$48.27	8.158%	$52.2079	$52.21	$52.20	$52.20
Purchase #2	$134.52	12.201%	$150.9328	$150.93	$150.95	$150.90
Purchase #3	$12.42	8.459%	$13.4706	$13.47	$13.45	$13.50
Purchase #4	$82.45	7.795%	$88.877	$88.88	$88.90	$88.90
Purchase #5	$160.71	7.327%	$172.4852	$172.49	$172.50	$172.50
Purchase #6	$177.88	6.102%	$188.7342	$188.73	$188.75	$188.70
Purchase #7	$212.49	4.552%	$222.1625	$222.16	$222.15	$222.20
7 purchase totals =	$828.74		$888.8702	$888.87	$888.90	$888.90