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	$90.90	5.712%	$96.0922	$96.09	$96.10	$96.10
Purchase #2	$104.32	6.553%	$111.1561	$111.16	$111.15	$111.20
Purchase #3	$114.27	3.810%	$118.6237	$118.62	$118.60	$118.60
Purchase #4	$184.53	13.745%	$209.8936	$209.89	$209.90	$209.90
Purchase #5	$214.31	12.245%	$240.5523	$240.55	$240.55	$240.60
Purchase #6	$6.37	6.529%	$6.7859	$6.79	$6.80	$6.80
Purchase #7	$152.71	8.779%	$166.1164	$166.12	$166.10	$166.10
7 purchase totals =	$867.41		$949.2202	$949.22	$949.20	$949.30