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	$114.27	10.403%	$126.1575	$126.16	$126.15	$126.20
Purchase #2	$82.92	4.206%	$86.4076	$86.41	$86.40	$86.40
Purchase #3	$7.71	11.865%	$8.6248	$8.62	$8.60	$8.60
Purchase #4	$69.34	4.219%	$72.2655	$72.27	$72.25	$72.30
Purchase #5	$171.75	11.826%	$192.0612	$192.06	$192.05	$192.10
Purchase #6	$84.51	8.464%	$91.6629	$91.66	$91.65	$91.70
Purchase #7	$90.28	11.596%	$100.7489	$100.75	$100.75	$100.70
7 purchase totals =	$620.78		$677.9284	$677.93	$677.85	$678.00