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	$9.76	13.534%	$11.0809	$11.08	$11.10	$11.10
Purchase #2	$86.37	6.166%	$91.6956	$91.70	$91.70	$91.70
Purchase #3	$172.82	7.357%	$185.5344	$185.53	$185.55	$185.50
Purchase #4	$125.81	13.103%	$142.2949	$142.29	$142.30	$142.30
Purchase #5	$33.72	10.672%	$37.3186	$37.32	$37.30	$37.30
Purchase #6	$35.73	12.575%	$40.223	$40.22	$40.20	$40.20
Purchase #7	$90.72	10.446%	$100.1966	$100.20	$100.20	$100.20
7 purchase totals =	$554.93		$608.3440	$608.34	$608.35	$608.30