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	$186.81	6.445%	$198.8499	$198.85	$198.85	$198.80
Purchase #2	$57.28	4.747%	$59.9991	$60.00	$60.00	$60.00
Purchase #3	$65.52	10.813%	$72.6047	$72.60	$72.60	$72.60
Purchase #4	$238.55	8.523%	$258.8816	$258.88	$258.90	$258.90
Purchase #5	$18.34	9.713%	$20.1214	$20.12	$20.10	$20.10
Purchase #6	$107.28	4.703%	$112.3254	$112.33	$112.35	$112.30
Purchase #7	$49.65	7.280%	$53.2645	$53.26	$53.25	$53.30
7 purchase totals =	$723.43		$776.0466	$776.04	$776.05	$776.00