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	$169.95	12.164%	$190.6227	$190.62	$190.60	$190.60
Purchase #2	$40.89	4.399%	$42.6888	$42.69	$42.70	$42.70
Purchase #3	$239.91	6.704%	$255.9936	$255.99	$256.00	$256.00
Purchase #4	$17.65	3.221%	$18.2185	$18.22	$18.20	$18.20
Purchase #5	$196.43	9.847%	$215.7725	$215.77	$215.75	$215.80
Purchase #6	$35.65	12.668%	$40.1661	$40.17	$40.15	$40.20
Purchase #7	$127.60	4.330%	$133.1251	$133.13	$133.15	$133.10
7 purchase totals =	$828.08		$896.5873	$896.59	$896.55	$896.60