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	$221.75	6.635%	$236.4631	$236.46	$236.45	$236.50
Purchase #2	$30.25	10.174%	$33.3276	$33.33	$33.35	$33.30
Purchase #3	$90.54	11.212%	$100.6913	$100.69	$100.70	$100.70
Purchase #4	$85.42	8.291%	$92.5022	$92.50	$92.50	$92.50
Purchase #5	$112.46	13.775%	$127.9514	$127.95	$127.95	$128.00
Purchase #6	$123.94	12.184%	$139.0408	$139.04	$139.05	$139.00
Purchase #7	$186.34	5.191%	$196.0129	$196.01	$196.00	$196.00
7 purchase totals =	$850.70		$925.9893	$925.98	$926.00	$926.00