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	$149.98	7.233%	$160.8281	$160.83	$160.85	$160.80
Purchase #2	$190.54	6.478%	$202.8832	$202.88	$202.90	$202.90
Purchase #3	$235.47	9.109%	$256.919	$256.92	$256.90	$256.90
Purchase #4	$76.61	9.214%	$83.6688	$83.67	$83.65	$83.70
Purchase #5	$172.84	4.390%	$180.4277	$180.43	$180.45	$180.40
Purchase #6	$41.97	4.717%	$43.9497	$43.95	$43.95	$43.90
Purchase #7	$81.61	8.385%	$88.453	$88.45	$88.45	$88.50
7 purchase totals =	$949.02		$1,017.1295	$1,017.13	$1,017.15	$1,017.10