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	$234.58	11.474%	$261.4957	$261.50	$261.50	$261.50
Purchase #2	$10.53	3.706%	$10.9202	$10.92	$10.90	$10.90
Purchase #3	$166.38	12.795%	$187.6683	$187.67	$187.65	$187.70
Purchase #4	$189.38	3.754%	$196.4893	$196.49	$196.50	$196.50
Purchase #5	$75.33	4.403%	$78.6468	$78.65	$78.65	$78.60
Purchase #6	$41.29	5.679%	$43.6349	$43.63	$43.65	$43.60
Purchase #7	$9.90	7.244%	$10.6172	$10.62	$10.60	$10.60
7 purchase totals =	$727.39		$789.4724	$789.48	$789.45	$789.40