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	$158.94	13.285%	$180.0552	$180.06	$180.05	$180.10
Purchase #2	$89.76	3.363%	$92.7786	$92.78	$92.80	$92.80
Purchase #3	$101.36	3.337%	$104.7424	$104.74	$104.75	$104.70
Purchase #4	$136.89	13.350%	$155.1648	$155.16	$155.15	$155.20
Purchase #5	$221.37	10.583%	$244.7976	$244.80	$244.80	$244.80
Purchase #6	$97.49	11.625%	$108.8232	$108.82	$108.80	$108.80
Purchase #7	$53.67	10.153%	$59.1191	$59.12	$59.10	$59.10
7 purchase totals =	$859.48		$945.4809	$945.48	$945.45	$945.50