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	$137.98	8.863%	$150.2092	$150.21	$150.20	$150.20
Purchase #2	$166.47	3.307%	$171.9752	$171.98	$172.00	$172.00
Purchase #3	$93.69	12.717%	$105.6046	$105.60	$105.60	$105.60
Purchase #4	$24.86	13.722%	$28.2713	$28.27	$28.25	$28.30
Purchase #5	$218.58	13.866%	$248.8883	$248.89	$248.90	$248.90
Purchase #6	$94.61	6.527%	$100.7852	$100.79	$100.80	$100.80
Purchase #7	$195.30	5.302%	$205.6548	$205.65	$205.65	$205.70
7 purchase totals =	$931.49		$1,011.3886	$1,011.39	$1,011.40	$1,011.50