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	$175.77	6.586%	$187.3462	$187.35	$187.35	$187.30
Purchase #2	$27.48	6.635%	$29.3033	$29.30	$29.30	$29.30
Purchase #3	$238.74	7.137%	$255.7789	$255.78	$255.80	$255.80
Purchase #4	$175.27	9.247%	$191.4772	$191.48	$191.50	$191.50
Purchase #5	$242.32	5.707%	$256.1492	$256.15	$256.15	$256.10
Purchase #6	$250.44	7.451%	$269.1003	$269.10	$269.10	$269.10
Purchase #7	$118.87	3.794%	$123.3799	$123.38	$123.40	$123.40
7 purchase totals =	$1,228.89		$1,312.5350	$1,312.54	$1,312.60	$1,312.50