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	$144.74	3.737%	$150.1489	$150.15	$150.15	$150.10
Purchase #2	$237.63	3.463%	$245.8591	$245.86	$245.85	$245.90
Purchase #3	$246.59	9.751%	$270.635	$270.64	$270.65	$270.60
Purchase #4	$10.32	5.325%	$10.8695	$10.87	$10.85	$10.90
Purchase #5	$49.72	12.504%	$55.937	$55.94	$55.95	$55.90
Purchase #6	$105.25	5.783%	$111.3366	$111.34	$111.35	$111.30
Purchase #7	$87.71	13.825%	$99.8359	$99.84	$99.85	$99.80
7 purchase totals =	$881.96		$944.6220	$944.64	$944.65	$944.50