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	$169.43	3.801%	$175.87	$175.87	$175.85	$175.90
Purchase #2	$169.45	9.636%	$185.7782	$185.78	$185.80	$185.80
Purchase #3	$99.26	12.441%	$111.6089	$111.61	$111.60	$111.60
Purchase #4	$198.79	5.592%	$209.9063	$209.91	$209.90	$209.90
Purchase #5	$117.82	13.598%	$133.8412	$133.84	$133.85	$133.80
Purchase #6	$249.54	4.151%	$259.8984	$259.90	$259.90	$259.90
Purchase #7	$198.51	3.649%	$205.7536	$205.75	$205.75	$205.80
7 purchase totals =	$1,202.80		$1,282.6566	$1,282.66	$1,282.65	$1,282.70