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	$243.52	4.155%	$253.6383	$253.64	$253.65	$253.60
Purchase #2	$11.41	4.794%	$11.957	$11.96	$11.95	$12.00
Purchase #3	$232.32	11.408%	$258.8231	$258.82	$258.80	$258.80
Purchase #4	$126.87	5.103%	$133.3442	$133.34	$133.35	$133.30
Purchase #5	$213.90	6.550%	$227.9105	$227.91	$227.90	$227.90
Purchase #6	$81.66	9.696%	$89.5778	$89.58	$89.60	$89.60
Purchase #7	$41.92	6.542%	$44.6624	$44.66	$44.65	$44.70
7 purchase totals =	$951.60		$1,019.9133	$1,019.91	$1,019.90	$1,019.90