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	$144.69	6.238%	$153.7158	$153.72	$153.70	$153.70
Purchase #2	$132.42	4.329%	$138.1525	$138.15	$138.15	$138.20
Purchase #3	$75.62	3.874%	$78.5495	$78.55	$78.55	$78.50
Purchase #4	$217.46	3.671%	$225.443	$225.44	$225.45	$225.40
Purchase #5	$73.39	3.641%	$76.0621	$76.06	$76.05	$76.10
Purchase #6	$53.28	11.498%	$59.4061	$59.41	$59.40	$59.40
Purchase #7	$92.67	13.324%	$105.0174	$105.02	$105.00	$105.00
7 purchase totals =	$789.53		$836.3464	$836.35	$836.30	$836.30