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	$60.25	7.585%	$64.82	$64.82	$64.80	$64.80
Purchase #2	$150.58	11.583%	$168.0217	$168.02	$168.00	$168.00
Purchase #3	$68.25	5.676%	$72.1239	$72.12	$72.10	$72.10
Purchase #4	$60.85	5.204%	$64.0166	$64.02	$64.00	$64.00
Purchase #5	$89.74	6.531%	$95.6009	$95.60	$95.60	$95.60
Purchase #6	$113.92	11.867%	$127.4389	$127.44	$127.45	$127.40
Purchase #7	$41.34	11.330%	$46.0238	$46.02	$46.00	$46.00
7 purchase totals =	$584.93		$638.0458	$638.04	$637.95	$637.90