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	$20.64	7.281%	$22.1428	$22.14	$22.15	$22.10
Purchase #2	$138.31	13.268%	$156.661	$156.66	$156.65	$156.70
Purchase #3	$143.80	4.376%	$150.0927	$150.09	$150.10	$150.10
Purchase #4	$139.92	4.605%	$146.3633	$146.36	$146.35	$146.40
Purchase #5	$218.28	10.249%	$240.6515	$240.65	$240.65	$240.70
Purchase #6	$235.86	5.269%	$248.2875	$248.29	$248.30	$248.30
Purchase #7	$49.57	4.668%	$51.8839	$51.88	$51.90	$51.90
7 purchase totals =	$946.38		$1,016.0827	$1,016.07	$1,016.10	$1,016.20