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	$141.90	7.312%	$152.2757	$152.28	$152.30	$152.30
Purchase #2	$24.45	13.802%	$27.8246	$27.82	$27.80	$27.80
Purchase #3	$241.64	5.587%	$255.1404	$255.14	$255.15	$255.10
Purchase #4	$76.87	8.415%	$83.3386	$83.34	$83.35	$83.30
Purchase #5	$98.76	5.779%	$104.4673	$104.47	$104.45	$104.50
Purchase #6	$78.89	11.467%	$87.9363	$87.94	$87.95	$87.90
Purchase #7	$203.66	9.252%	$222.5026	$222.50	$222.50	$222.50
7 purchase totals =	$866.17		$933.4855	$933.49	$933.50	$933.40