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	$88.80	8.341%	$96.2068	$96.21	$96.20	$96.20
Purchase #2	$215.32	3.239%	$222.2942	$222.29	$222.30	$222.30
Purchase #3	$132.72	11.536%	$148.0306	$148.03	$148.05	$148.00
Purchase #4	$57.53	3.513%	$59.551	$59.55	$59.55	$59.60
Purchase #5	$142.77	13.500%	$162.044	$162.04	$162.05	$162.00
Purchase #6	$79.42	5.639%	$83.8985	$83.90	$83.90	$83.90
Purchase #7	$130.61	10.686%	$144.567	$144.57	$144.55	$144.60
7 purchase totals =	$847.17		$916.5921	$916.59	$916.60	$916.60