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	$100.28	4.842%	$105.1356	$105.14	$105.15	$105.10
Purchase #2	$9.32	10.793%	$10.3259	$10.33	$10.35	$10.30
Purchase #3	$203.78	10.515%	$225.2075	$225.21	$225.20	$225.20
Purchase #4	$36.42	5.771%	$38.5218	$38.52	$38.50	$38.50
Purchase #5	$213.38	8.497%	$231.5109	$231.51	$231.50	$231.50
Purchase #6	$97.30	3.593%	$100.796	$100.80	$100.80	$100.80
Purchase #7	$206.28	13.405%	$233.9318	$233.93	$233.95	$233.90
7 purchase totals =	$866.76		$945.4295	$945.44	$945.45	$945.30