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	$51.92	11.498%	$57.8898	$57.89	$57.90	$57.90
Purchase #2	$195.74	4.659%	$204.8595	$204.86	$204.85	$204.90
Purchase #3	$77.57	10.220%	$85.4977	$85.50	$85.50	$85.50
Purchase #4	$176.77	13.234%	$200.1637	$200.16	$200.15	$200.20
Purchase #5	$230.90	5.673%	$243.999	$244.00	$244.00	$244.00
Purchase #6	$173.65	9.668%	$190.4385	$190.44	$190.45	$190.40
Purchase #7	$149.86	5.826%	$158.5908	$158.59	$158.60	$158.60
7 purchase totals =	$1,056.41		$1,141.4390	$1,141.44	$1,141.45	$1,141.50