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	$72.45	11.747%	$80.9607	$80.96	$80.95	$81.00
Purchase #2	$152.33	13.577%	$173.0118	$173.01	$173.00	$173.00
Purchase #3	$227.62	10.665%	$251.8957	$251.90	$251.90	$251.90
Purchase #4	$11.56	4.463%	$12.0759	$12.08	$12.10	$12.10
Purchase #5	$152.81	8.586%	$165.9303	$165.93	$165.95	$165.90
Purchase #6	$216.97	3.187%	$223.8848	$223.88	$223.90	$223.90
Purchase #7	$155.28	11.695%	$173.44	$173.44	$173.45	$173.40
7 purchase totals =	$989.02		$1,081.1992	$1,081.20	$1,081.25	$1,081.20