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	$92.29	8.819%	$100.4291	$100.43	$100.45	$100.40
Purchase #2	$136.71	5.513%	$144.2468	$144.25	$144.25	$144.20
Purchase #3	$186.74	5.335%	$196.7026	$196.70	$196.70	$196.70
Purchase #4	$95.59	11.143%	$106.2416	$106.24	$106.25	$106.20
Purchase #5	$215.50	6.498%	$229.5032	$229.50	$229.50	$229.50
Purchase #6	$74.30	5.508%	$78.3924	$78.39	$78.40	$78.40
Purchase #7	$13.93	12.491%	$15.67	$15.67	$15.65	$15.70
7 purchase totals =	$815.06		$871.1857	$871.18	$871.20	$871.10