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	$141.92	5.212%	$149.3169	$149.32	$149.30	$149.30
Purchase #2	$29.32	6.602%	$31.2557	$31.26	$31.25	$31.30
Purchase #3	$222.44	13.533%	$252.5428	$252.54	$252.55	$252.50
Purchase #4	$250.77	12.179%	$281.3113	$281.31	$281.30	$281.30
Purchase #5	$90.70	12.769%	$102.2815	$102.28	$102.30	$102.30
Purchase #6	$219.78	6.277%	$233.5756	$233.58	$233.60	$233.60
Purchase #7	$37.73	13.225%	$42.7198	$42.72	$42.70	$42.70
7 purchase totals =	$992.66		$1,093.0036	$1,093.01	$1,093.00	$1,093.00