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	$129.91	10.705%	$143.8169	$143.82	$143.80	$143.80
Purchase #2	$152.35	13.371%	$172.7207	$172.72	$172.70	$172.70
Purchase #3	$12.93	11.211%	$14.3796	$14.38	$14.40	$14.40
Purchase #4	$220.26	13.585%	$250.1823	$250.18	$250.20	$250.20
Purchase #5	$82.48	5.259%	$86.8176	$86.82	$86.80	$86.80
Purchase #6	$88.30	6.477%	$94.0192	$94.02	$94.00	$94.00
Purchase #7	$247.69	10.585%	$273.908	$273.91	$273.90	$273.90
7 purchase totals =	$933.92		$1,035.8443	$1,035.85	$1,035.80	$1,035.80