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	$191.50	13.614%	$217.5708	$217.57	$217.55	$217.60
Purchase #2	$115.70	5.517%	$122.0832	$122.08	$122.10	$122.10
Purchase #3	$244.52	11.438%	$272.4882	$272.49	$272.50	$272.50
Purchase #4	$185.73	12.823%	$209.5462	$209.55	$209.55	$209.50
Purchase #5	$41.72	9.174%	$45.5474	$45.55	$45.55	$45.50
Purchase #6	$123.87	5.357%	$130.5057	$130.51	$130.50	$130.50
Purchase #7	$147.48	10.389%	$162.8017	$162.80	$162.80	$162.80
7 purchase totals =	$1,050.52		$1,160.5432	$1,160.55	$1,160.55	$1,160.50