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	$235.62	10.183%	$259.6132	$259.61	$259.60	$259.60
Purchase #2	$193.56	11.585%	$215.9839	$215.98	$216.00	$216.00
Purchase #3	$175.50	11.751%	$196.123	$196.12	$196.10	$196.10
Purchase #4	$170.80	3.401%	$176.6089	$176.61	$176.60	$176.60
Purchase #5	$14.79	5.212%	$15.5609	$15.56	$15.55	$15.60
Purchase #6	$14.41	5.547%	$15.2093	$15.21	$15.20	$15.20
Purchase #7	$15.89	3.562%	$16.456	$16.46	$16.45	$16.50
7 purchase totals =	$820.57		$895.5552	$895.55	$895.50	$895.60