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	$34.54	5.522%	$36.4473	$36.45	$36.45	$36.40
Purchase #2	$51.73	10.228%	$57.0209	$57.02	$57.00	$57.00
Purchase #3	$17.67	6.336%	$18.7896	$18.79	$18.80	$18.80
Purchase #4	$169.81	6.456%	$180.7729	$180.77	$180.75	$180.80
Purchase #5	$59.42	11.551%	$66.2836	$66.28	$66.30	$66.30
Purchase #6	$191.99	4.583%	$200.7889	$200.79	$200.80	$200.80
Purchase #7	$7.43	6.615%	$7.9215	$7.92	$7.90	$7.90
7 purchase totals =	$532.59		$568.0247	$568.02	$568.00	$568.00