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	$63.33	10.408%	$69.9214	$69.92	$69.90	$69.90
Purchase #2	$199.82	11.220%	$222.2398	$222.24	$222.25	$222.20
Purchase #3	$15.41	11.426%	$17.1707	$17.17	$17.15	$17.20
Purchase #4	$152.55	9.301%	$166.7387	$166.74	$166.75	$166.70
Purchase #5	$131.98	10.670%	$146.0623	$146.06	$146.05	$146.10
Purchase #6	$50.26	10.629%	$55.6021	$55.60	$55.60	$55.60
Purchase #7	$52.99	12.720%	$59.7303	$59.73	$59.75	$59.70
7 purchase totals =	$666.34		$737.4653	$737.46	$737.45	$737.40