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	$219.65	4.857%	$230.3184	$230.32	$230.30	$230.30
Purchase #2	$38.44	3.229%	$39.6812	$39.68	$39.70	$39.70
Purchase #3	$29.25	7.528%	$31.4519	$31.45	$31.45	$31.50
Purchase #4	$247.82	9.559%	$271.5091	$271.51	$271.50	$271.50
Purchase #5	$183.67	4.731%	$192.3594	$192.36	$192.35	$192.40
Purchase #6	$153.25	10.194%	$168.8723	$168.87	$168.85	$168.90
Purchase #7	$59.51	9.438%	$65.1266	$65.13	$65.15	$65.10
7 purchase totals =	$931.59		$999.3189	$999.32	$999.30	$999.40