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	$154.73	12.466%	$174.0186	$174.02	$174.00	$174.00
Purchase #2	$222.58	3.150%	$229.5913	$229.59	$229.60	$229.60
Purchase #3	$164.68	4.509%	$172.1054	$172.11	$172.10	$172.10
Purchase #4	$169.86	12.281%	$190.7205	$190.72	$190.70	$190.70
Purchase #5	$92.30	4.151%	$96.1314	$96.13	$96.15	$96.10
Purchase #6	$29.74	3.195%	$30.6902	$30.69	$30.70	$30.70
Purchase #7	$137.79	10.480%	$152.2304	$152.23	$152.25	$152.20
7 purchase totals =	$971.68		$1,045.4878	$1,045.49	$1,045.50	$1,045.40