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	$91.88	13.480%	$104.2654	$104.27	$104.25	$104.30
Purchase #2	$97.41	5.808%	$103.0676	$103.07	$103.05	$103.10
Purchase #3	$52.80	3.103%	$54.4384	$54.44	$54.45	$54.40
Purchase #4	$12.35	4.432%	$12.8974	$12.90	$12.90	$12.90
Purchase #5	$67.82	12.280%	$76.1483	$76.15	$76.15	$76.10
Purchase #6	$72.55	6.675%	$77.3927	$77.39	$77.40	$77.40
Purchase #7	$42.69	13.218%	$48.3328	$48.33	$48.35	$48.30
7 purchase totals =	$437.50		$476.5426	$476.55	$476.55	$476.50