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	$196.51	10.673%	$217.4835	$217.48	$217.50	$217.50
Purchase #2	$91.57	12.730%	$103.2269	$103.23	$103.25	$103.20
Purchase #3	$50.66	11.545%	$56.5087	$56.51	$56.50	$56.50
Purchase #4	$201.62	6.676%	$215.0802	$215.08	$215.10	$215.10
Purchase #5	$32.33	4.194%	$33.6859	$33.69	$33.70	$33.70
Purchase #6	$69.65	12.376%	$78.2699	$78.27	$78.25	$78.30
Purchase #7	$158.70	6.590%	$169.1583	$169.16	$169.15	$169.20
7 purchase totals =	$801.04		$873.4134	$873.42	$873.45	$873.50