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	$143.64	4.449%	$150.0305	$150.03	$150.05	$150.00
Purchase #2	$46.81	9.274%	$51.1512	$51.15	$51.15	$51.20
Purchase #3	$49.37	11.864%	$55.2273	$55.23	$55.25	$55.20
Purchase #4	$100.43	13.106%	$113.5924	$113.59	$113.60	$113.60
Purchase #5	$120.41	5.645%	$127.2071	$127.21	$127.20	$127.20
Purchase #6	$220.77	10.207%	$243.304	$243.30	$243.30	$243.30
Purchase #7	$141.96	6.711%	$151.4869	$151.49	$151.50	$151.50
7 purchase totals =	$823.39		$891.9994	$892.00	$892.05	$892.00