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	$243.45	8.742%	$264.7324	$264.73	$264.75	$264.70
Purchase #2	$244.64	7.851%	$263.8467	$263.85	$263.85	$263.80
Purchase #3	$66.50	6.509%	$70.8285	$70.83	$70.85	$70.80
Purchase #4	$48.83	9.109%	$53.2779	$53.28	$53.30	$53.30
Purchase #5	$196.33	8.584%	$213.183	$213.18	$213.20	$213.20
Purchase #6	$167.49	7.759%	$180.4855	$180.49	$180.50	$180.50
Purchase #7	$200.72	8.186%	$217.1509	$217.15	$217.15	$217.20
7 purchase totals =	$1,167.96		$1,263.5049	$1,263.51	$1,263.60	$1,263.50