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	$114.80	7.773%	$123.7234	$123.72	$123.70	$123.70
Purchase #2	$48.28	4.543%	$50.4734	$50.47	$50.45	$50.50
Purchase #3	$95.57	11.862%	$106.9065	$106.91	$106.90	$106.90
Purchase #4	$45.49	8.498%	$49.3557	$49.36	$49.35	$49.40
Purchase #5	$132.33	13.654%	$150.3983	$150.40	$150.40	$150.40
Purchase #6	$116.77	9.297%	$127.6261	$127.63	$127.65	$127.60
Purchase #7	$240.86	3.703%	$249.779	$249.78	$249.80	$249.80
7 purchase totals =	$794.10		$858.2624	$858.27	$858.25	$858.30