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	$117.32	5.491%	$123.762	$123.76	$123.75	$123.80
Purchase #2	$226.28	8.373%	$245.2264	$245.23	$245.25	$245.20
Purchase #3	$109.80	12.580%	$123.6128	$123.61	$123.60	$123.60
Purchase #4	$225.69	8.339%	$244.5103	$244.51	$244.50	$244.50
Purchase #5	$83.29	7.629%	$89.6442	$89.64	$89.65	$89.60
Purchase #6	$104.91	6.690%	$111.9285	$111.93	$111.95	$111.90
Purchase #7	$70.92	5.770%	$75.0121	$75.01	$75.00	$75.00
7 purchase totals =	$938.21		$1,013.6963	$1,013.69	$1,013.70	$1,013.60