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	$60.57	3.177%	$62.4943	$62.49	$62.50	$62.50
Purchase #2	$126.50	11.651%	$141.2385	$141.24	$141.25	$141.20
Purchase #3	$153.66	12.542%	$172.932	$172.93	$172.95	$172.90
Purchase #4	$221.67	12.478%	$249.33	$249.33	$249.35	$249.30
Purchase #5	$19.78	6.189%	$21.0042	$21.00	$21.00	$21.00
Purchase #6	$142.48	4.292%	$148.5952	$148.60	$148.60	$148.60
Purchase #7	$190.42	8.363%	$206.3448	$206.34	$206.35	$206.30
7 purchase totals =	$915.08		$1,001.9390	$1,001.93	$1,002.00	$1,001.80