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	$175.69	5.337%	$185.0666	$185.07	$185.05	$185.10
Purchase #2	$81.75	8.434%	$88.6448	$88.64	$88.65	$88.60
Purchase #3	$153.53	10.607%	$169.8149	$169.81	$169.80	$169.80
Purchase #4	$94.47	6.383%	$100.5	$100.50	$100.50	$100.50
Purchase #5	$112.47	4.664%	$117.7156	$117.72	$117.70	$117.70
Purchase #6	$203.72	9.491%	$223.0551	$223.06	$223.05	$223.10
Purchase #7	$246.80	7.268%	$264.7374	$264.74	$264.75	$264.70
7 purchase totals =	$1,068.43		$1,149.5344	$1,149.54	$1,149.50	$1,149.50