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	$95.90	13.665%	$109.0047	$109.00	$109.00	$109.00
Purchase #2	$159.59	11.841%	$178.4871	$178.49	$178.50	$178.50
Purchase #3	$79.59	10.644%	$88.0616	$88.06	$88.05	$88.10
Purchase #4	$10.49	9.227%	$11.4579	$11.46	$11.45	$11.50
Purchase #5	$159.64	3.136%	$164.6463	$164.65	$164.65	$164.60
Purchase #6	$102.43	3.603%	$106.1206	$106.12	$106.10	$106.10
Purchase #7	$246.29	10.164%	$271.3229	$271.32	$271.30	$271.30
7 purchase totals =	$853.93		$929.1011	$929.10	$929.05	$929.10