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	$109.98	11.300%	$122.4077	$122.41	$122.40	$122.40
Purchase #2	$9.66	9.726%	$10.5995	$10.60	$10.60	$10.60
Purchase #3	$100.69	12.455%	$113.2309	$113.23	$113.25	$113.20
Purchase #4	$19.59	12.821%	$22.1016	$22.10	$22.10	$22.10
Purchase #5	$89.60	13.238%	$101.4612	$101.46	$101.45	$101.50
Purchase #6	$78.76	12.123%	$88.3081	$88.31	$88.30	$88.30
Purchase #7	$138.68	10.670%	$153.4772	$153.48	$153.50	$153.50
7 purchase totals =	$546.96		$611.5862	$611.59	$611.60	$611.60