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	$98.69	6.401%	$105.0071	$105.01	$105.00	$105.00
Purchase #2	$126.42	10.425%	$139.5993	$139.60	$139.60	$139.60
Purchase #3	$165.33	4.285%	$172.4144	$172.41	$172.40	$172.40
Purchase #4	$116.93	5.606%	$123.4851	$123.49	$123.50	$123.50
Purchase #5	$113.68	6.218%	$120.7486	$120.75	$120.75	$120.70
Purchase #6	$240.76	5.442%	$253.8622	$253.86	$253.85	$253.90
Purchase #7	$177.97	6.448%	$189.4455	$189.45	$189.45	$189.40
7 purchase totals =	$1,039.78		$1,104.5622	$1,104.57	$1,104.55	$1,104.50