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	$99.34	9.745%	$109.0207	$109.02	$109.00	$109.00
Purchase #2	$158.38	6.666%	$168.9376	$168.94	$168.95	$168.90
Purchase #3	$145.67	3.205%	$150.3387	$150.34	$150.35	$150.30
Purchase #4	$103.56	7.457%	$111.2825	$111.28	$111.30	$111.30
Purchase #5	$211.84	4.853%	$222.1206	$222.12	$222.10	$222.10
Purchase #6	$149.87	6.856%	$160.1451	$160.15	$160.15	$160.10
Purchase #7	$31.46	9.734%	$34.5223	$34.52	$34.50	$34.50
7 purchase totals =	$900.12		$956.3675	$956.37	$956.35	$956.20