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	$32.42	13.556%	$36.8149	$36.81	$36.80	$36.80
Purchase #2	$66.32	13.319%	$75.1532	$75.15	$75.15	$75.20
Purchase #3	$54.92	8.220%	$59.4344	$59.43	$59.45	$59.40
Purchase #4	$212.60	13.317%	$240.9119	$240.91	$240.90	$240.90
Purchase #5	$144.87	5.343%	$152.6104	$152.61	$152.60	$152.60
Purchase #6	$217.75	13.855%	$247.9193	$247.92	$247.90	$247.90
Purchase #7	$57.64	6.696%	$61.4996	$61.50	$61.50	$61.50
7 purchase totals =	$786.52		$874.3437	$874.33	$874.30	$874.30