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	$83.72	8.133%	$90.5289	$90.53	$90.55	$90.50
Purchase #2	$16.88	3.489%	$17.4689	$17.47	$17.45	$17.50
Purchase #3	$92.37	13.252%	$104.6109	$104.61	$104.60	$104.60
Purchase #4	$224.66	5.569%	$237.1713	$237.17	$237.15	$237.20
Purchase #5	$110.68	12.581%	$124.6047	$124.60	$124.60	$124.60
Purchase #6	$96.48	8.268%	$104.457	$104.46	$104.45	$104.50
Purchase #7	$78.78	4.451%	$82.2865	$82.29	$82.30	$82.30
7 purchase totals =	$703.57		$761.1282	$761.13	$761.10	$761.20