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	$187.55	4.687%	$196.3405	$196.34	$196.35	$196.30
Purchase #2	$244.38	11.231%	$271.8263	$271.83	$271.85	$271.80
Purchase #3	$198.44	13.684%	$225.5945	$225.59	$225.60	$225.60
Purchase #4	$12.74	4.182%	$13.2728	$13.27	$13.25	$13.30
Purchase #5	$22.85	11.628%	$25.507	$25.51	$25.50	$25.50
Purchase #6	$16.39	12.219%	$18.3927	$18.39	$18.40	$18.40
Purchase #7	$220.98	12.717%	$249.082	$249.08	$249.10	$249.10
7 purchase totals =	$903.33		$1,000.0158	$1,000.01	$1,000.05	$1,000.00