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	$112.57	9.697%	$123.4859	$123.49	$123.50	$123.50
Purchase #2	$188.29	4.360%	$196.4994	$196.50	$196.50	$196.50
Purchase #3	$83.78	12.305%	$94.0891	$94.09	$94.10	$94.10
Purchase #4	$52.32	4.117%	$54.474	$54.47	$54.45	$54.50
Purchase #5	$104.80	5.568%	$110.6353	$110.64	$110.65	$110.60
Purchase #6	$53.86	10.200%	$59.3537	$59.35	$59.35	$59.40
Purchase #7	$84.66	12.407%	$95.1638	$95.16	$95.15	$95.20
7 purchase totals =	$680.28		$733.7012	$733.70	$733.70	$733.80