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	$166.73	3.165%	$172.007	$172.01	$172.00	$172.00
Purchase #2	$14.77	12.816%	$16.6629	$16.66	$16.65	$16.70
Purchase #3	$120.92	13.213%	$136.8972	$136.90	$136.90	$136.90
Purchase #4	$177.25	12.343%	$199.128	$199.13	$199.15	$199.10
Purchase #5	$95.62	10.621%	$105.7758	$105.78	$105.80	$105.80
Purchase #6	$164.77	12.741%	$185.7633	$185.76	$185.75	$185.80
Purchase #7	$139.87	9.544%	$153.2192	$153.22	$153.20	$153.20
7 purchase totals =	$879.93		$969.4534	$969.46	$969.45	$969.50