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	$106.36	7.445%	$114.2785	$114.28	$114.30	$114.30
Purchase #2	$201.64	10.102%	$222.0097	$222.01	$222.00	$222.00
Purchase #3	$95.74	3.815%	$99.3925	$99.39	$99.40	$99.40
Purchase #4	$132.33	4.861%	$138.7626	$138.76	$138.75	$138.80
Purchase #5	$115.31	10.253%	$127.1327	$127.13	$127.15	$127.10
Purchase #6	$228.33	11.105%	$253.686	$253.69	$253.70	$253.70
Purchase #7	$109.71	6.250%	$116.5669	$116.57	$116.55	$116.60
7 purchase totals =	$989.42		$1,071.8289	$1,071.83	$1,071.85	$1,071.90