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	$115.90	6.694%	$123.6583	$123.66	$123.65	$123.70
Purchase #2	$241.88	10.437%	$267.125	$267.13	$267.15	$267.10
Purchase #3	$105.26	7.579%	$113.2377	$113.24	$113.25	$113.20
Purchase #4	$76.47	11.704%	$85.42	$85.42	$85.40	$85.40
Purchase #5	$81.73	11.536%	$91.1584	$91.16	$91.15	$91.20
Purchase #6	$85.27	13.342%	$96.6467	$96.65	$96.65	$96.60
Purchase #7	$157.89	6.393%	$167.9839	$167.98	$168.00	$168.00
7 purchase totals =	$864.40		$945.2300	$945.24	$945.25	$945.20