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	$132.83	7.439%	$142.7112	$142.71	$142.70	$142.70
Purchase #2	$210.61	9.800%	$231.2498	$231.25	$231.25	$231.20
Purchase #3	$59.90	3.742%	$62.1415	$62.14	$62.15	$62.10
Purchase #4	$32.32	9.372%	$35.349	$35.35	$35.35	$35.30
Purchase #5	$88.37	5.103%	$92.8795	$92.88	$92.90	$92.90
Purchase #6	$137.64	10.388%	$151.938	$151.94	$151.95	$151.90
Purchase #7	$197.76	11.834%	$221.1629	$221.16	$221.15	$221.20
7 purchase totals =	$859.43		$937.4319	$937.43	$937.45	$937.30