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	$231.32	13.231%	$261.9259	$261.93	$261.95	$261.90
Purchase #2	$9.27	13.309%	$10.5037	$10.50	$10.50	$10.50
Purchase #3	$51.34	5.504%	$54.1658	$54.17	$54.15	$54.20
Purchase #4	$173.96	13.147%	$196.8305	$196.83	$196.85	$196.80
Purchase #5	$173.91	6.390%	$185.0228	$185.02	$185.00	$185.00
Purchase #6	$40.95	12.336%	$46.0016	$46.00	$46.00	$46.00
Purchase #7	$148.47	4.760%	$155.5372	$155.54	$155.55	$155.50
7 purchase totals =	$829.22		$909.9875	$909.99	$910.00	$909.90