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	$80.74	7.448%	$86.7535	$86.75	$86.75	$86.80
Purchase #2	$24.33	4.533%	$25.4329	$25.43	$25.45	$25.40
Purchase #3	$134.38	8.758%	$146.149	$146.15	$146.15	$146.10
Purchase #4	$153.99	5.371%	$162.2608	$162.26	$162.25	$162.30
Purchase #5	$112.25	13.394%	$127.2848	$127.28	$127.30	$127.30
Purchase #6	$220.95	3.662%	$229.0412	$229.04	$229.05	$229.00
Purchase #7	$200.27	7.626%	$215.5426	$215.54	$215.55	$215.50
7 purchase totals =	$926.91		$992.4648	$992.45	$992.50	$992.40