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	$100.58	11.135%	$111.7796	$111.78	$111.80	$111.80
Purchase #2	$16.40	3.735%	$17.0125	$17.01	$17.00	$17.00
Purchase #3	$216.76	9.749%	$237.8919	$237.89	$237.90	$237.90
Purchase #4	$56.90	6.343%	$60.5092	$60.51	$60.50	$60.50
Purchase #5	$153.25	11.685%	$171.1573	$171.16	$171.15	$171.20
Purchase #6	$62.29	7.697%	$67.0845	$67.08	$67.10	$67.10
Purchase #7	$196.74	9.296%	$215.029	$215.03	$215.05	$215.00
7 purchase totals =	$802.92		$880.4640	$880.46	$880.50	$880.50