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	$70.39	11.128%	$78.223	$78.22	$78.20	$78.20
Purchase #2	$122.49	8.666%	$133.105	$133.11	$133.10	$133.10
Purchase #3	$158.72	8.612%	$172.389	$172.39	$172.40	$172.40
Purchase #4	$68.61	4.372%	$71.6096	$71.61	$71.60	$71.60
Purchase #5	$240.49	13.254%	$272.3645	$272.36	$272.35	$272.40
Purchase #6	$184.59	13.781%	$210.0283	$210.03	$210.05	$210.00
Purchase #7	$69.95	3.439%	$72.3556	$72.36	$72.35	$72.40
7 purchase totals =	$915.24		$1,010.0750	$1,010.08	$1,010.05	$1,010.10