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	$64.77	9.618%	$70.9996	$71.00	$71.00	$71.00
Purchase #2	$14.30	12.475%	$16.0839	$16.08	$16.10	$16.10
Purchase #3	$47.87	7.576%	$51.4966	$51.50	$51.50	$51.50
Purchase #4	$170.28	11.221%	$189.3871	$189.39	$189.40	$189.40
Purchase #5	$36.61	13.575%	$41.5798	$41.58	$41.60	$41.60
Purchase #6	$173.31	13.345%	$196.4382	$196.44	$196.45	$196.40
Purchase #7	$56.79	8.417%	$61.57	$61.57	$61.55	$61.60
7 purchase totals =	$563.93		$627.5552	$627.56	$627.60	$627.60