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	$231.73	3.748%	$240.4152	$240.42	$240.40	$240.40
Purchase #2	$53.66	13.256%	$60.7732	$60.77	$60.75	$60.80
Purchase #3	$117.45	8.433%	$127.3546	$127.35	$127.35	$127.40
Purchase #4	$48.52	9.159%	$52.9639	$52.96	$52.95	$53.00
Purchase #5	$209.26	11.107%	$232.5025	$232.50	$232.50	$232.50
Purchase #6	$204.55	8.536%	$222.0104	$222.01	$222.00	$222.00
Purchase #7	$168.73	4.186%	$175.793	$175.79	$175.80	$175.80
7 purchase totals =	$1,033.90		$1,111.8128	$1,111.80	$1,111.75	$1,111.90