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	$13.26	9.620%	$14.5356	$14.54	$14.55	$14.50
Purchase #2	$83.38	8.552%	$90.5107	$90.51	$90.50	$90.50
Purchase #3	$31.89	4.352%	$33.2779	$33.28	$33.30	$33.30
Purchase #4	$233.68	11.311%	$260.1115	$260.11	$260.10	$260.10
Purchase #5	$249.69	13.229%	$282.7215	$282.72	$282.70	$282.70
Purchase #6	$29.67	10.369%	$32.7465	$32.75	$32.75	$32.70
Purchase #7	$174.65	7.379%	$187.5374	$187.54	$187.55	$187.50
7 purchase totals =	$816.22		$901.4411	$901.45	$901.45	$901.30