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	$144.41	12.204%	$162.0338	$162.03	$162.05	$162.00
Purchase #2	$64.65	9.318%	$70.6741	$70.67	$70.65	$70.70
Purchase #3	$178.36	8.781%	$194.0218	$194.02	$194.00	$194.00
Purchase #4	$131.95	10.541%	$145.8588	$145.86	$145.85	$145.90
Purchase #5	$97.98	13.578%	$111.2837	$111.28	$111.30	$111.30
Purchase #6	$68.50	11.746%	$76.546	$76.55	$76.55	$76.50
Purchase #7	$40.79	4.111%	$42.4669	$42.47	$42.45	$42.50
7 purchase totals =	$726.64		$802.8851	$802.88	$802.85	$802.90