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	$227.33	12.268%	$255.2188	$255.22	$255.20	$255.20
Purchase #2	$65.79	10.593%	$72.7591	$72.76	$72.75	$72.80
Purchase #3	$104.38	7.444%	$112.15	$112.15	$112.15	$112.20
Purchase #4	$169.46	5.393%	$178.599	$178.60	$178.60	$178.60
Purchase #5	$166.64	8.531%	$180.8561	$180.86	$180.85	$180.90
Purchase #6	$172.55	10.237%	$190.2139	$190.21	$190.20	$190.20
Purchase #7	$153.58	11.439%	$171.148	$171.15	$171.15	$171.10
7 purchase totals =	$1,059.73		$1,160.9449	$1,160.95	$1,160.90	$1,161.00