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	$30.81	3.322%	$31.8335	$31.83	$31.85	$31.80
Purchase #2	$121.47	9.408%	$132.8979	$132.90	$132.90	$132.90
Purchase #3	$18.83	5.409%	$19.8485	$19.85	$19.85	$19.80
Purchase #4	$86.72	6.219%	$92.1131	$92.11	$92.10	$92.10
Purchase #5	$95.70	10.435%	$105.6863	$105.69	$105.70	$105.70
Purchase #6	$196.56	11.644%	$219.4474	$219.45	$219.45	$219.40
Purchase #7	$144.57	4.261%	$150.7301	$150.73	$150.75	$150.70
7 purchase totals =	$694.66		$752.5568	$752.56	$752.60	$752.40