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	$91.30	12.631%	$102.8321	$102.83	$102.85	$102.80
Purchase #2	$57.96	7.337%	$62.2125	$62.21	$62.20	$62.20
Purchase #3	$90.37	11.365%	$100.6406	$100.64	$100.65	$100.60
Purchase #4	$196.59	4.629%	$205.6902	$205.69	$205.70	$205.70
Purchase #5	$249.47	3.731%	$258.7777	$258.78	$258.80	$258.80
Purchase #6	$183.45	11.575%	$204.6843	$204.68	$204.70	$204.70
Purchase #7	$65.66	12.296%	$73.7336	$73.73	$73.75	$73.70
7 purchase totals =	$934.80		$1,008.5710	$1,008.56	$1,008.65	$1,008.50