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	$10.59	9.473%	$11.5932	$11.59	$11.60	$11.60
Purchase #2	$47.99	6.226%	$50.9779	$50.98	$51.00	$51.00
Purchase #3	$161.41	6.637%	$172.1228	$172.12	$172.10	$172.10
Purchase #4	$90.72	10.552%	$100.2928	$100.29	$100.30	$100.30
Purchase #5	$133.33	3.314%	$137.7486	$137.75	$137.75	$137.70
Purchase #6	$159.68	5.421%	$168.3363	$168.34	$168.35	$168.30
Purchase #7	$48.89	3.369%	$50.5371	$50.54	$50.55	$50.50
7 purchase totals =	$652.61		$691.6087	$691.61	$691.65	$691.50