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	$152.67	12.634%	$171.9583	$171.96	$171.95	$172.00
Purchase #2	$203.84	11.442%	$227.1634	$227.16	$227.15	$227.20
Purchase #3	$208.40	7.184%	$223.3715	$223.37	$223.35	$223.40
Purchase #4	$42.71	8.831%	$46.4817	$46.48	$46.50	$46.50
Purchase #5	$131.87	11.346%	$146.832	$146.83	$146.85	$146.80
Purchase #6	$59.64	9.372%	$65.2295	$65.23	$65.25	$65.20
Purchase #7	$231.74	4.608%	$242.4186	$242.42	$242.40	$242.40
7 purchase totals =	$1,030.87		$1,123.4550	$1,123.45	$1,123.45	$1,123.50