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	$95.83	5.264%	$100.8745	$100.87	$100.85	$100.90
Purchase #2	$130.93	10.814%	$145.0888	$145.09	$145.10	$145.10
Purchase #3	$194.62	5.477%	$205.2793	$205.28	$205.30	$205.30
Purchase #4	$161.92	7.866%	$174.6566	$174.66	$174.65	$174.70
Purchase #5	$5.51	5.808%	$5.83	$5.83	$5.85	$5.80
Purchase #6	$170.72	6.224%	$181.3456	$181.35	$181.35	$181.30
Purchase #7	$186.50	5.508%	$196.7724	$196.77	$196.75	$196.80
7 purchase totals =	$946.03		$1,009.8472	$1,009.85	$1,009.85	$1,009.90