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	$104.89	6.686%	$111.9029	$111.90	$111.90	$111.90
Purchase #2	$100.28	13.557%	$113.875	$113.88	$113.90	$113.90
Purchase #3	$207.94	4.704%	$217.7215	$217.72	$217.70	$217.70
Purchase #4	$159.34	8.177%	$172.3692	$172.37	$172.35	$172.40
Purchase #5	$188.67	3.641%	$195.5395	$195.54	$195.55	$195.50
Purchase #6	$170.41	7.293%	$182.838	$182.84	$182.85	$182.80
Purchase #7	$172.70	10.538%	$190.8991	$190.90	$190.90	$190.90
7 purchase totals =	$1,104.23		$1,185.1452	$1,185.15	$1,185.15	$1,185.10