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	$35.84	5.367%	$37.7635	$37.76	$37.75	$37.80
Purchase #2	$23.43	4.707%	$24.5329	$24.53	$24.55	$24.50
Purchase #3	$101.82	9.492%	$111.4848	$111.48	$111.50	$111.50
Purchase #4	$207.61	10.512%	$229.434	$229.43	$229.45	$229.40
Purchase #5	$18.83	13.775%	$21.4238	$21.42	$21.40	$21.40
Purchase #6	$228.31	9.501%	$250.0017	$250.00	$250.00	$250.00
Purchase #7	$144.72	8.347%	$156.7998	$156.80	$156.80	$156.80
7 purchase totals =	$760.56		$831.4405	$831.42	$831.45	$831.40