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	$118.85	4.129%	$123.7573	$123.76	$123.75	$123.80
Purchase #2	$196.59	8.813%	$213.9155	$213.92	$213.90	$213.90
Purchase #3	$53.41	5.700%	$56.4544	$56.45	$56.45	$56.50
Purchase #4	$219.83	9.747%	$241.2568	$241.26	$241.25	$241.30
Purchase #5	$229.39	5.355%	$241.6738	$241.67	$241.65	$241.70
Purchase #6	$94.82	9.835%	$104.1455	$104.15	$104.15	$104.10
Purchase #7	$62.35	13.561%	$70.8053	$70.81	$70.80	$70.80
7 purchase totals =	$975.24		$1,052.0086	$1,052.02	$1,051.95	$1,052.10