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	$114.52	11.716%	$127.9372	$127.94	$127.95	$127.90
Purchase #2	$57.41	4.403%	$59.9378	$59.94	$59.95	$59.90
Purchase #3	$248.98	4.662%	$260.5874	$260.59	$260.60	$260.60
Purchase #4	$234.91	13.617%	$266.8977	$266.90	$266.90	$266.90
Purchase #5	$88.70	11.639%	$99.0238	$99.02	$99.00	$99.00
Purchase #6	$94.54	10.287%	$104.2653	$104.27	$104.25	$104.30
Purchase #7	$137.40	4.284%	$143.2862	$143.29	$143.30	$143.30
7 purchase totals =	$976.46		$1,061.9354	$1,061.95	$1,061.95	$1,061.90