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	$44.45	7.604%	$47.83	$47.83	$47.85	$47.80
Purchase #2	$129.62	13.792%	$147.4972	$147.50	$147.50	$147.50
Purchase #3	$78.64	8.482%	$85.3102	$85.31	$85.30	$85.30
Purchase #4	$128.71	8.873%	$140.1304	$140.13	$140.15	$140.10
Purchase #5	$50.89	4.459%	$53.1592	$53.16	$53.15	$53.20
Purchase #6	$13.87	8.839%	$15.096	$15.10	$15.10	$15.10
Purchase #7	$11.75	5.847%	$12.437	$12.44	$12.45	$12.40
7 purchase totals =	$457.93		$501.4600	$501.47	$501.50	$501.40