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	$76.42	11.164%	$84.9515	$84.95	$84.95	$85.00
Purchase #2	$53.93	9.417%	$59.0086	$59.01	$59.00	$59.00
Purchase #3	$33.85	10.832%	$37.5166	$37.52	$37.50	$37.50
Purchase #4	$149.33	6.416%	$158.911	$158.91	$158.90	$158.90
Purchase #5	$242.76	7.283%	$260.4402	$260.44	$260.45	$260.40
Purchase #6	$90.85	5.669%	$96.0003	$96.00	$96.00	$96.00
Purchase #7	$125.32	5.706%	$132.4708	$132.47	$132.45	$132.50
7 purchase totals =	$772.46		$829.2990	$829.30	$829.25	$829.30