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	$174.28	9.358%	$190.5891	$190.59	$190.60	$190.60
Purchase #2	$170.51	12.682%	$192.1341	$192.13	$192.15	$192.10
Purchase #3	$198.52	10.432%	$219.2296	$219.23	$219.25	$219.20
Purchase #4	$135.54	12.245%	$152.1369	$152.14	$152.15	$152.10
Purchase #5	$130.94	9.522%	$143.4081	$143.41	$143.40	$143.40
Purchase #6	$52.75	6.376%	$56.1133	$56.11	$56.10	$56.10
Purchase #7	$116.60	12.782%	$131.5038	$131.50	$131.50	$131.50
7 purchase totals =	$979.14		$1,085.1149	$1,085.11	$1,085.15	$1,085.00