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	$143.69	7.417%	$154.3475	$154.35	$154.35	$154.30
Purchase #2	$238.32	6.760%	$254.4304	$254.43	$254.45	$254.40
Purchase #3	$111.95	10.551%	$123.7618	$123.76	$123.75	$123.80
Purchase #4	$127.95	10.128%	$140.9088	$140.91	$140.90	$140.90
Purchase #5	$34.34	9.509%	$37.6054	$37.61	$37.60	$37.60
Purchase #6	$27.38	6.112%	$29.0535	$29.05	$29.05	$29.10
Purchase #7	$192.79	5.824%	$204.0181	$204.02	$204.00	$204.00
7 purchase totals =	$876.42		$944.1255	$944.13	$944.10	$944.10