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	$160.89	11.540%	$179.4567	$179.46	$179.45	$179.50
Purchase #2	$93.76	13.714%	$106.6182	$106.62	$106.60	$106.60
Purchase #3	$241.98	5.631%	$255.6059	$255.61	$255.60	$255.60
Purchase #4	$139.61	12.759%	$157.4228	$157.42	$157.40	$157.40
Purchase #5	$246.86	8.278%	$267.2951	$267.30	$267.30	$267.30
Purchase #6	$24.36	10.316%	$26.873	$26.87	$26.85	$26.90
Purchase #7	$90.64	12.426%	$101.9029	$101.90	$101.90	$101.90
7 purchase totals =	$998.10		$1,095.1746	$1,095.18	$1,095.10	$1,095.20