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	$111.61	10.556%	$123.3916	$123.39	$123.40	$123.40
Purchase #2	$164.37	10.504%	$181.6354	$181.64	$181.65	$181.60
Purchase #3	$140.98	6.222%	$149.7518	$149.75	$149.75	$149.80
Purchase #4	$24.81	13.595%	$28.1829	$28.18	$28.20	$28.20
Purchase #5	$32.91	13.503%	$37.3538	$37.35	$37.35	$37.40
Purchase #6	$115.73	3.161%	$119.3882	$119.39	$119.40	$119.40
Purchase #7	$94.93	10.685%	$105.0733	$105.07	$105.05	$105.10
7 purchase totals =	$685.34		$744.7770	$744.77	$744.80	$744.90