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	$12.60	4.862%	$13.2126	$13.21	$13.20	$13.20
Purchase #2	$120.92	10.391%	$133.4848	$133.48	$133.50	$133.50
Purchase #3	$45.80	5.640%	$48.3831	$48.38	$48.40	$48.40
Purchase #4	$184.78	6.334%	$196.484	$196.48	$196.50	$196.50
Purchase #5	$52.45	6.162%	$55.682	$55.68	$55.70	$55.70
Purchase #6	$198.83	4.781%	$208.3361	$208.34	$208.35	$208.30
Purchase #7	$74.83	4.454%	$78.1629	$78.16	$78.15	$78.20
7 purchase totals =	$690.21		$733.7455	$733.73	$733.80	$733.80