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	$98.46	13.666%	$111.9155	$111.92	$111.90	$111.90
Purchase #2	$18.70	12.304%	$21.0008	$21.00	$21.00	$21.00
Purchase #3	$97.25	4.606%	$101.7293	$101.73	$101.75	$101.70
Purchase #4	$206.29	12.225%	$231.509	$231.51	$231.50	$231.50
Purchase #5	$225.80	3.748%	$234.263	$234.26	$234.25	$234.30
Purchase #6	$159.34	7.789%	$171.751	$171.75	$171.75	$171.80
Purchase #7	$135.59	6.246%	$144.059	$144.06	$144.05	$144.10
7 purchase totals =	$941.43		$1,016.2276	$1,016.23	$1,016.20	$1,016.30