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	$217.31	4.219%	$226.4783	$226.48	$226.50	$226.50
Purchase #2	$152.79	9.700%	$167.6106	$167.61	$167.60	$167.60
Purchase #3	$136.80	4.410%	$142.8329	$142.83	$142.85	$142.80
Purchase #4	$59.69	7.861%	$64.3822	$64.38	$64.40	$64.40
Purchase #5	$154.31	8.491%	$167.4125	$167.41	$167.40	$167.40
Purchase #6	$170.85	5.145%	$179.6402	$179.64	$179.65	$179.60
Purchase #7	$246.94	11.664%	$275.7431	$275.74	$275.75	$275.70
7 purchase totals =	$1,138.69		$1,224.0998	$1,224.09	$1,224.15	$1,224.00