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	$169.84	3.434%	$175.6723	$175.67	$175.65	$175.70
Purchase #2	$211.29	9.505%	$231.3731	$231.37	$231.35	$231.40
Purchase #3	$93.35	11.254%	$103.8556	$103.86	$103.85	$103.90
Purchase #4	$134.31	10.382%	$148.2541	$148.25	$148.25	$148.30
Purchase #5	$64.60	10.746%	$71.5419	$71.54	$71.55	$71.50
Purchase #6	$176.87	3.242%	$182.6041	$182.60	$182.60	$182.60
Purchase #7	$39.88	5.696%	$42.1516	$42.15	$42.15	$42.20
7 purchase totals =	$890.14		$955.4527	$955.44	$955.40	$955.60