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	$214.65	8.395%	$232.6699	$232.67	$232.65	$232.70
Purchase #2	$16.40	7.682%	$17.6598	$17.66	$17.65	$17.70
Purchase #3	$78.72	13.565%	$89.3984	$89.40	$89.40	$89.40
Purchase #4	$74.89	13.653%	$85.1147	$85.11	$85.10	$85.10
Purchase #5	$29.74	10.541%	$32.8749	$32.87	$32.85	$32.90
Purchase #6	$19.32	8.780%	$21.0163	$21.02	$21.00	$21.00
Purchase #7	$38.76	10.777%	$42.9372	$42.94	$42.95	$42.90
7 purchase totals =	$472.48		$521.6712	$521.67	$521.60	$521.70