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	$43.36	13.697%	$49.299	$49.30	$49.30	$49.30
Purchase #2	$40.54	7.550%	$43.6008	$43.60	$43.60	$43.60
Purchase #3	$207.70	12.360%	$233.3717	$233.37	$233.35	$233.40
Purchase #4	$207.52	4.736%	$217.3481	$217.35	$217.35	$217.30
Purchase #5	$247.44	11.252%	$275.2819	$275.28	$275.30	$275.30
Purchase #6	$194.25	6.198%	$206.2896	$206.29	$206.30	$206.30
Purchase #7	$67.69	5.370%	$71.325	$71.33	$71.35	$71.30
7 purchase totals =	$1,008.50		$1,096.5161	$1,096.52	$1,096.55	$1,096.50