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	$156.81	9.659%	$171.9563	$171.96	$171.95	$172.00
Purchase #2	$219.94	4.388%	$229.591	$229.59	$229.60	$229.60
Purchase #3	$143.90	11.362%	$160.2499	$160.25	$160.25	$160.20
Purchase #4	$152.70	9.644%	$167.4264	$167.43	$167.45	$167.40
Purchase #5	$177.92	12.814%	$200.7187	$200.72	$200.70	$200.70
Purchase #6	$10.91	4.343%	$11.3838	$11.38	$11.40	$11.40
Purchase #7	$18.91	11.771%	$21.1359	$21.14	$21.15	$21.10
7 purchase totals =	$881.09		$962.4620	$962.47	$962.50	$962.40