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	$51.90	3.749%	$53.8457	$53.85	$53.85	$53.80
Purchase #2	$172.73	4.642%	$180.7481	$180.75	$180.75	$180.70
Purchase #3	$220.68	9.733%	$242.1588	$242.16	$242.15	$242.20
Purchase #4	$65.51	10.810%	$72.5916	$72.59	$72.60	$72.60
Purchase #5	$69.96	3.771%	$72.5982	$72.60	$72.60	$72.60
Purchase #6	$107.57	4.420%	$112.3246	$112.32	$112.30	$112.30
Purchase #7	$83.89	3.348%	$86.6986	$86.70	$86.70	$86.70
7 purchase totals =	$772.24		$820.9656	$820.97	$820.95	$820.90