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	$75.55	9.315%	$82.5875	$82.59	$82.60	$82.60
Purchase #2	$111.93	7.526%	$120.3539	$120.35	$120.35	$120.40
Purchase #3	$14.38	3.264%	$14.8494	$14.85	$14.85	$14.80
Purchase #4	$74.73	4.120%	$77.8089	$77.81	$77.80	$77.80
Purchase #5	$227.56	11.306%	$253.2879	$253.29	$253.30	$253.30
Purchase #6	$162.42	4.364%	$169.508	$169.51	$169.50	$169.50
Purchase #7	$72.88	4.472%	$76.1392	$76.14	$76.15	$76.10
7 purchase totals =	$739.45		$794.5348	$794.54	$794.55	$794.50