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	$37.54	9.695%	$41.1795	$41.18	$41.20	$41.20
Purchase #2	$198.87	9.184%	$217.1342	$217.13	$217.15	$217.10
Purchase #3	$142.87	3.112%	$147.3161	$147.32	$147.30	$147.30
Purchase #4	$198.64	5.388%	$209.3427	$209.34	$209.35	$209.30
Purchase #5	$169.58	13.387%	$192.2817	$192.28	$192.30	$192.30
Purchase #6	$153.67	5.739%	$162.4891	$162.49	$162.50	$162.50
Purchase #7	$100.64	3.847%	$104.5116	$104.51	$104.50	$104.50
7 purchase totals =	$1,001.81		$1,074.2549	$1,074.25	$1,074.30	$1,074.20