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	$152.80	11.408%	$170.2314	$170.23	$170.25	$170.20
Purchase #2	$47.49	10.176%	$52.3226	$52.32	$52.30	$52.30
Purchase #3	$32.49	5.677%	$34.3345	$34.33	$34.35	$34.30
Purchase #4	$169.44	10.407%	$187.0736	$187.07	$187.05	$187.10
Purchase #5	$166.79	5.288%	$175.6099	$175.61	$175.60	$175.60
Purchase #6	$41.55	10.136%	$45.7615	$45.76	$45.75	$45.80
Purchase #7	$80.45	11.644%	$89.8176	$89.82	$89.80	$89.80
7 purchase totals =	$691.01		$755.1511	$755.14	$755.10	$755.10