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	$38.58	12.130%	$43.2598	$43.26	$43.25	$43.30
Purchase #2	$70.88	10.503%	$78.3245	$78.32	$78.30	$78.30
Purchase #3	$76.58	11.224%	$85.1753	$85.18	$85.20	$85.20
Purchase #4	$40.61	7.575%	$43.6862	$43.69	$43.70	$43.70
Purchase #5	$193.64	10.195%	$213.3816	$213.38	$213.40	$213.40
Purchase #6	$124.86	3.602%	$129.3575	$129.36	$129.35	$129.40
Purchase #7	$89.33	13.616%	$101.4932	$101.49	$101.50	$101.50
7 purchase totals =	$634.48		$694.6781	$694.68	$694.70	$694.80