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	$207.55	8.499%	$225.1897	$225.19	$225.20	$225.20
Purchase #2	$43.52	6.593%	$46.3893	$46.39	$46.40	$46.40
Purchase #3	$111.84	10.301%	$123.3606	$123.36	$123.35	$123.40
Purchase #4	$215.70	11.712%	$240.9628	$240.96	$240.95	$241.00
Purchase #5	$226.72	7.828%	$244.4676	$244.47	$244.45	$244.50
Purchase #6	$196.61	8.298%	$212.9247	$212.92	$212.90	$212.90
Purchase #7	$36.74	3.821%	$38.1438	$38.14	$38.15	$38.10
7 purchase totals =	$1,038.68		$1,131.4385	$1,131.43	$1,131.40	$1,131.50