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	$162.28	12.631%	$182.7776	$182.78	$182.80	$182.80
Purchase #2	$239.43	12.398%	$269.1145	$269.11	$269.10	$269.10
Purchase #3	$222.86	13.621%	$253.2158	$253.22	$253.20	$253.20
Purchase #4	$65.55	10.726%	$72.5809	$72.58	$72.60	$72.60
Purchase #5	$7.32	4.695%	$7.6637	$7.66	$7.65	$7.70
Purchase #6	$205.96	12.302%	$231.2972	$231.30	$231.30	$231.30
Purchase #7	$125.37	11.154%	$139.3538	$139.35	$139.35	$139.40
7 purchase totals =	$1,028.77		$1,156.0035	$1,156.00	$1,156.00	$1,156.10