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	$78.43	11.480%	$87.4338	$87.43	$87.45	$87.40
Purchase #2	$240.41	3.791%	$249.5239	$249.52	$249.50	$249.50
Purchase #3	$118.83	4.268%	$123.9017	$123.90	$123.90	$123.90
Purchase #4	$184.42	6.661%	$196.7042	$196.70	$196.70	$196.70
Purchase #5	$90.74	5.569%	$95.7933	$95.79	$95.80	$95.80
Purchase #6	$83.91	10.281%	$92.5368	$92.54	$92.55	$92.50
Purchase #7	$183.57	12.798%	$207.0633	$207.06	$207.05	$207.10
7 purchase totals =	$980.31		$1,052.9570	$1,052.94	$1,052.95	$1,052.90