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	$242.52	4.839%	$254.2555	$254.26	$254.25	$254.30
Purchase #2	$145.41	5.642%	$153.614	$153.61	$153.60	$153.60
Purchase #3	$225.63	3.725%	$234.0347	$234.03	$234.05	$234.00
Purchase #4	$167.86	10.553%	$185.5743	$185.57	$185.55	$185.60
Purchase #5	$82.82	6.291%	$88.0302	$88.03	$88.05	$88.00
Purchase #6	$18.92	8.797%	$20.5844	$20.58	$20.60	$20.60
Purchase #7	$152.49	5.412%	$160.7428	$160.74	$160.75	$160.70
7 purchase totals =	$1,035.65		$1,096.8359	$1,096.82	$1,096.85	$1,096.80