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	$146.91	9.607%	$161.0236	$161.02	$161.00	$161.00
Purchase #2	$115.65	8.513%	$125.4953	$125.50	$125.50	$125.50
Purchase #3	$71.51	9.727%	$78.4658	$78.47	$78.45	$78.50
Purchase #4	$79.44	11.858%	$88.86	$88.86	$88.85	$88.90
Purchase #5	$95.45	5.635%	$100.8286	$100.83	$100.85	$100.80
Purchase #6	$233.54	3.317%	$241.2865	$241.29	$241.30	$241.30
Purchase #7	$159.87	13.425%	$181.3325	$181.33	$181.35	$181.30
7 purchase totals =	$902.37		$977.2923	$977.30	$977.30	$977.30