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	$243.51	12.699%	$274.4333	$274.43	$274.45	$274.40
Purchase #2	$209.71	11.445%	$233.7113	$233.71	$233.70	$233.70
Purchase #3	$109.28	4.784%	$114.508	$114.51	$114.50	$114.50
Purchase #4	$87.61	5.346%	$92.2936	$92.29	$92.30	$92.30
Purchase #5	$174.63	13.784%	$198.701	$198.70	$198.70	$198.70
Purchase #6	$97.57	5.581%	$103.0154	$103.02	$103.00	$103.00
Purchase #7	$13.51	7.505%	$14.5239	$14.52	$14.50	$14.50
7 purchase totals =	$935.82		$1,031.1865	$1,031.18	$1,031.15	$1,031.10