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	$216.49	6.810%	$231.233	$231.23	$231.25	$231.20
Purchase #2	$8.88	8.111%	$9.6003	$9.60	$9.60	$9.60
Purchase #3	$181.42	8.131%	$196.1713	$196.17	$196.15	$196.20
Purchase #4	$94.61	8.680%	$102.8221	$102.82	$102.80	$102.80
Purchase #5	$121.51	6.663%	$129.6062	$129.61	$129.60	$129.60
Purchase #6	$74.69	3.763%	$77.5006	$77.50	$77.50	$77.50
Purchase #7	$37.32	11.135%	$41.4756	$41.48	$41.50	$41.50
7 purchase totals =	$734.92		$788.4091	$788.41	$788.40	$788.40