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	$159.59	7.866%	$172.1433	$172.14	$172.15	$172.10
Purchase #2	$213.76	12.824%	$241.1726	$241.17	$241.15	$241.20
Purchase #3	$67.37	8.165%	$72.8708	$72.87	$72.85	$72.90
Purchase #4	$148.90	7.349%	$159.8427	$159.84	$159.85	$159.80
Purchase #5	$223.78	5.727%	$236.5959	$236.60	$236.60	$236.60
Purchase #6	$186.43	3.273%	$192.5319	$192.53	$192.55	$192.50
Purchase #7	$162.27	6.559%	$172.9133	$172.91	$172.90	$172.90
7 purchase totals =	$1,162.10		$1,248.0705	$1,248.06	$1,248.05	$1,248.00