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	$96.45	8.388%	$104.5402	$104.54	$104.55	$104.50
Purchase #2	$153.39	4.136%	$159.7342	$159.73	$159.75	$159.70
Purchase #3	$129.72	11.870%	$145.1178	$145.12	$145.10	$145.10
Purchase #4	$28.33	11.129%	$31.4828	$31.48	$31.50	$31.50
Purchase #5	$158.30	12.732%	$178.4548	$178.45	$178.45	$178.50
Purchase #6	$76.41	5.283%	$80.4467	$80.45	$80.45	$80.40
Purchase #7	$164.86	3.402%	$170.4685	$170.47	$170.45	$170.50
7 purchase totals =	$807.46		$870.2450	$870.24	$870.25	$870.20