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	$76.85	13.456%	$87.1909	$87.19	$87.20	$87.20
Purchase #2	$82.78	7.789%	$89.2277	$89.23	$89.25	$89.20
Purchase #3	$57.69	3.525%	$59.7236	$59.72	$59.70	$59.70
Purchase #4	$205.33	3.769%	$213.0689	$213.07	$213.05	$213.10
Purchase #5	$11.87	5.131%	$12.479	$12.48	$12.50	$12.50
Purchase #6	$79.30	4.382%	$82.7749	$82.77	$82.75	$82.80
Purchase #7	$15.70	13.823%	$17.8702	$17.87	$17.85	$17.90
7 purchase totals =	$529.52		$562.3352	$562.33	$562.30	$562.40