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	$104.30	9.797%	$114.5183	$114.52	$114.50	$114.50
Purchase #2	$225.90	10.341%	$249.2603	$249.26	$249.25	$249.30
Purchase #3	$78.75	4.122%	$81.9961	$82.00	$82.00	$82.00
Purchase #4	$125.83	4.111%	$131.0029	$131.00	$131.00	$131.00
Purchase #5	$200.65	10.184%	$221.0842	$221.08	$221.10	$221.10
Purchase #6	$135.48	13.247%	$153.427	$153.43	$153.45	$153.40
Purchase #7	$118.74	4.116%	$123.6273	$123.63	$123.65	$123.60
7 purchase totals =	$989.65		$1,074.9161	$1,074.92	$1,074.95	$1,074.90