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	$126.41	11.843%	$141.3807	$141.38	$141.40	$141.40
Purchase #2	$182.44	9.712%	$200.1586	$200.16	$200.15	$200.20
Purchase #3	$99.89	9.243%	$109.1228	$109.12	$109.10	$109.10
Purchase #4	$153.84	9.690%	$168.7471	$168.75	$168.75	$168.70
Purchase #5	$17.58	9.494%	$19.249	$19.25	$19.25	$19.20
Purchase #6	$140.35	13.644%	$159.4994	$159.50	$159.50	$159.50
Purchase #7	$160.56	3.671%	$166.4542	$166.45	$166.45	$166.50
7 purchase totals =	$881.07		$964.6118	$964.61	$964.60	$964.60