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	$107.68	13.364%	$122.0704	$122.07	$122.05	$122.10
Purchase #2	$72.86	9.446%	$79.7424	$79.74	$79.75	$79.70
Purchase #3	$32.56	7.699%	$35.0668	$35.07	$35.05	$35.10
Purchase #4	$104.86	6.549%	$111.7273	$111.73	$111.75	$111.70
Purchase #5	$172.83	7.286%	$185.4224	$185.42	$185.40	$185.40
Purchase #6	$86.47	5.631%	$91.3391	$91.34	$91.35	$91.30
Purchase #7	$86.27	6.503%	$91.8801	$91.88	$91.90	$91.90
7 purchase totals =	$663.53		$717.2485	$717.25	$717.25	$717.20