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	$34.61	8.144%	$37.4286	$37.43	$37.45	$37.40
Purchase #2	$122.76	9.366%	$134.2577	$134.26	$134.25	$134.30
Purchase #3	$203.35	9.689%	$223.0526	$223.05	$223.05	$223.10
Purchase #4	$10.90	10.172%	$12.0087	$12.01	$12.00	$12.00
Purchase #5	$51.70	13.357%	$58.6056	$58.61	$58.60	$58.60
Purchase #6	$88.53	13.799%	$100.7463	$100.75	$100.75	$100.70
Purchase #7	$210.53	5.513%	$222.1365	$222.14	$222.15	$222.10
7 purchase totals =	$722.38		$788.2360	$788.25	$788.25	$788.20