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	$187.37	4.661%	$196.1033	$196.10	$196.10	$196.10
Purchase #2	$225.52	8.606%	$244.9283	$244.93	$244.95	$244.90
Purchase #3	$113.76	12.227%	$127.6694	$127.67	$127.65	$127.70
Purchase #4	$143.43	12.839%	$161.845	$161.85	$161.85	$161.80
Purchase #5	$24.78	4.415%	$25.874	$25.87	$25.85	$25.90
Purchase #6	$187.95	9.317%	$205.4613	$205.46	$205.45	$205.50
Purchase #7	$113.78	3.238%	$117.4642	$117.46	$117.45	$117.50
7 purchase totals =	$996.59		$1,079.3455	$1,079.34	$1,079.30	$1,079.40