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	$157.66	12.144%	$176.8062	$176.81	$176.80	$176.80
Purchase #2	$210.25	6.119%	$223.1152	$223.12	$223.10	$223.10
Purchase #3	$30.95	4.438%	$32.3236	$32.32	$32.30	$32.30
Purchase #4	$55.76	11.627%	$62.2432	$62.24	$62.25	$62.20
Purchase #5	$127.35	7.377%	$136.7446	$136.74	$136.75	$136.70
Purchase #6	$130.86	12.237%	$146.8733	$146.87	$146.85	$146.90
Purchase #7	$154.78	5.150%	$162.7512	$162.75	$162.75	$162.80
7 purchase totals =	$867.61		$940.8573	$940.85	$940.80	$940.80