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	$182.33	4.624%	$190.7609	$190.76	$190.75	$190.80
Purchase #2	$190.77	10.255%	$210.3335	$210.33	$210.35	$210.30
Purchase #3	$78.83	6.107%	$83.6441	$83.64	$83.65	$83.60
Purchase #4	$149.44	7.328%	$160.391	$160.39	$160.40	$160.40
Purchase #5	$233.69	10.189%	$257.5007	$257.50	$257.50	$257.50
Purchase #6	$234.92	9.303%	$256.7746	$256.77	$256.75	$256.80
Purchase #7	$246.30	8.433%	$267.0705	$267.07	$267.05	$267.10
7 purchase totals =	$1,316.28		$1,426.4753	$1,426.46	$1,426.45	$1,426.50