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	$196.52	13.297%	$222.6513	$222.65	$222.65	$222.70
Purchase #2	$230.40	12.746%	$259.7668	$259.77	$259.75	$259.80
Purchase #3	$71.88	13.386%	$81.5019	$81.50	$81.50	$81.50
Purchase #4	$170.72	10.591%	$188.801	$188.80	$188.80	$188.80
Purchase #5	$146.40	12.282%	$164.3808	$164.38	$164.40	$164.40
Purchase #6	$225.59	5.576%	$238.1689	$238.17	$238.15	$238.20
Purchase #7	$174.61	3.587%	$180.8733	$180.87	$180.85	$180.90
7 purchase totals =	$1,216.12		$1,336.1440	$1,336.14	$1,336.10	$1,336.30