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	$216.82	7.303%	$232.6544	$232.65	$232.65	$232.70
Purchase #2	$62.36	3.456%	$64.5152	$64.52	$64.50	$64.50
Purchase #3	$243.59	4.518%	$254.5954	$254.60	$254.60	$254.60
Purchase #4	$38.87	8.378%	$42.1265	$42.13	$42.15	$42.10
Purchase #5	$50.80	6.296%	$53.9984	$54.00	$54.00	$54.00
Purchase #6	$70.36	6.778%	$75.129	$75.13	$75.15	$75.10
Purchase #7	$241.53	5.728%	$255.3648	$255.36	$255.35	$255.40
7 purchase totals =	$924.33		$978.3837	$978.39	$978.40	$978.40