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	$189.55	5.297%	$199.5905	$199.59	$199.60	$199.60
Purchase #2	$10.42	11.565%	$11.6251	$11.63	$11.65	$11.60
Purchase #3	$116.59	11.429%	$129.9151	$129.92	$129.90	$129.90
Purchase #4	$215.86	3.240%	$222.8539	$222.85	$222.85	$222.90
Purchase #5	$93.45	13.350%	$105.9256	$105.93	$105.95	$105.90
Purchase #6	$155.57	7.490%	$167.2222	$167.22	$167.20	$167.20
Purchase #7	$212.36	3.445%	$219.6758	$219.68	$219.70	$219.70
7 purchase totals =	$993.80		$1,056.8082	$1,056.82	$1,056.85	$1,056.80