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	$151.25	7.208%	$162.1521	$162.15	$162.15	$162.20
Purchase #2	$175.41	8.275%	$189.9252	$189.93	$189.95	$189.90
Purchase #3	$165.82	5.385%	$174.7494	$174.75	$174.75	$174.70
Purchase #4	$120.41	10.115%	$132.5895	$132.59	$132.60	$132.60
Purchase #5	$214.40	11.376%	$238.7901	$238.79	$238.80	$238.80
Purchase #6	$88.33	4.670%	$92.455	$92.46	$92.45	$92.50
Purchase #7	$212.55	10.329%	$234.5043	$234.50	$234.50	$234.50
7 purchase totals =	$1,128.17		$1,225.1656	$1,225.17	$1,225.20	$1,225.20