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	$205.45	12.683%	$231.5072	$231.51	$231.50	$231.50
Purchase #2	$185.54	7.493%	$199.4425	$199.44	$199.45	$199.40
Purchase #3	$220.37	13.328%	$249.7409	$249.74	$249.75	$249.70
Purchase #4	$52.35	13.647%	$59.4942	$59.49	$59.50	$59.50
Purchase #5	$23.62	4.395%	$24.6581	$24.66	$24.65	$24.70
Purchase #6	$141.93	8.610%	$154.1502	$154.15	$154.15	$154.20
Purchase #7	$78.46	8.657%	$85.2523	$85.25	$85.25	$85.30
7 purchase totals =	$907.72		$1,004.2454	$1,004.24	$1,004.25	$1,004.30