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	$233.44	11.167%	$259.5082	$259.51	$259.50	$259.50
Purchase #2	$151.89	13.517%	$172.421	$172.42	$172.40	$172.40
Purchase #3	$147.48	10.129%	$162.4182	$162.42	$162.40	$162.40
Purchase #4	$159.38	6.289%	$169.4034	$169.40	$169.40	$169.40
Purchase #5	$205.42	11.469%	$228.9796	$228.98	$229.00	$229.00
Purchase #6	$230.59	3.550%	$238.7759	$238.78	$238.80	$238.80
Purchase #7	$144.57	5.832%	$153.0013	$153.00	$153.00	$153.00
7 purchase totals =	$1,272.77		$1,384.5076	$1,384.51	$1,384.50	$1,384.50