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	$99.73	12.655%	$112.3508	$112.35	$112.35	$112.40
Purchase #2	$230.68	13.800%	$262.5138	$262.51	$262.50	$262.50
Purchase #3	$246.82	3.729%	$256.0239	$256.02	$256.00	$256.00
Purchase #4	$46.69	10.860%	$51.7605	$51.76	$51.75	$51.80
Purchase #5	$72.66	13.120%	$82.193	$82.19	$82.20	$82.20
Purchase #6	$140.57	10.381%	$155.1626	$155.16	$155.15	$155.20
Purchase #7	$136.52	10.791%	$151.2519	$151.25	$151.25	$151.30
7 purchase totals =	$973.67		$1,071.2565	$1,071.24	$1,071.20	$1,071.40