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	$244.50	9.775%	$268.3999	$268.40	$268.40	$268.40
Purchase #2	$12.63	6.645%	$13.4693	$13.47	$13.45	$13.50
Purchase #3	$175.72	10.419%	$194.0283	$194.03	$194.05	$194.00
Purchase #4	$162.25	6.867%	$173.3917	$173.39	$173.40	$173.40
Purchase #5	$138.79	4.183%	$144.5956	$144.60	$144.60	$144.60
Purchase #6	$56.28	9.241%	$61.4808	$61.48	$61.50	$61.50
Purchase #7	$54.27	8.874%	$59.0859	$59.09	$59.10	$59.10
7 purchase totals =	$844.44		$914.4515	$914.46	$914.50	$914.50