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	$89.25	6.798%	$95.3172	$95.32	$95.30	$95.30
Purchase #2	$115.63	12.608%	$130.2086	$130.21	$130.20	$130.20
Purchase #3	$132.88	3.504%	$137.5361	$137.54	$137.55	$137.50
Purchase #4	$87.64	13.367%	$99.3548	$99.35	$99.35	$99.40
Purchase #5	$123.49	3.486%	$127.7949	$127.79	$127.80	$127.80
Purchase #6	$175.66	10.597%	$194.2747	$194.27	$194.25	$194.30
Purchase #7	$239.70	12.239%	$269.0369	$269.04	$269.05	$269.00
7 purchase totals =	$964.25		$1,053.5232	$1,053.52	$1,053.50	$1,053.50