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	$65.28	9.588%	$71.539	$71.54	$71.55	$71.50
Purchase #2	$80.61	6.283%	$85.6747	$85.67	$85.65	$85.70
Purchase #3	$54.71	8.769%	$59.5075	$59.51	$59.50	$59.50
Purchase #4	$68.37	13.323%	$77.4789	$77.48	$77.50	$77.50
Purchase #5	$32.71	3.474%	$33.8463	$33.85	$33.85	$33.80
Purchase #6	$229.99	10.461%	$254.0493	$254.05	$254.05	$254.00
Purchase #7	$186.92	9.795%	$205.2288	$205.23	$205.25	$205.20
7 purchase totals =	$718.59		$787.3245	$787.33	$787.35	$787.20