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	$171.53	9.420%	$187.6881	$187.69	$187.70	$187.70
Purchase #2	$108.74	13.612%	$123.5417	$123.54	$123.55	$123.50
Purchase #3	$198.69	8.348%	$215.2766	$215.28	$215.30	$215.30
Purchase #4	$138.70	3.398%	$143.413	$143.41	$143.40	$143.40
Purchase #5	$105.26	7.284%	$112.9271	$112.93	$112.95	$112.90
Purchase #6	$179.62	9.378%	$196.4648	$196.46	$196.45	$196.50
Purchase #7	$89.70	10.273%	$98.9149	$98.91	$98.90	$98.90
7 purchase totals =	$992.24		$1,078.2262	$1,078.22	$1,078.25	$1,078.20