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	$158.93	11.298%	$176.8859	$176.89	$176.90	$176.90
Purchase #2	$47.45	7.102%	$50.8199	$50.82	$50.80	$50.80
Purchase #3	$77.25	13.150%	$87.4084	$87.41	$87.40	$87.40
Purchase #4	$95.90	3.145%	$98.9161	$98.92	$98.90	$98.90
Purchase #5	$141.64	8.200%	$153.2545	$153.25	$153.25	$153.30
Purchase #6	$79.62	4.808%	$83.4481	$83.45	$83.45	$83.40
Purchase #7	$94.88	11.112%	$105.4231	$105.42	$105.40	$105.40
7 purchase totals =	$695.67		$756.1560	$756.16	$756.10	$756.10