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	$211.85	9.231%	$231.4059	$231.41	$231.40	$231.40
Purchase #2	$54.94	8.324%	$59.5132	$59.51	$59.50	$59.50
Purchase #3	$131.26	10.431%	$144.9517	$144.95	$144.95	$145.00
Purchase #4	$144.47	5.572%	$152.5199	$152.52	$152.50	$152.50
Purchase #5	$63.33	7.581%	$68.131	$68.13	$68.15	$68.10
Purchase #6	$91.77	9.560%	$100.5432	$100.54	$100.55	$100.50
Purchase #7	$105.34	7.198%	$112.9224	$112.92	$112.90	$112.90
7 purchase totals =	$802.96		$869.9873	$869.98	$869.95	$869.90