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	$111.48	11.209%	$123.9758	$123.98	$124.00	$124.00
Purchase #2	$162.86	11.217%	$181.128	$181.13	$181.15	$181.10
Purchase #3	$172.82	3.579%	$179.0052	$179.01	$179.00	$179.00
Purchase #4	$203.83	5.781%	$215.6134	$215.61	$215.60	$215.60
Purchase #5	$104.53	6.519%	$111.3443	$111.34	$111.35	$111.30
Purchase #6	$166.66	3.610%	$172.6764	$172.68	$172.70	$172.70
Purchase #7	$113.60	11.641%	$126.8242	$126.82	$126.80	$126.80
7 purchase totals =	$1,035.78		$1,110.5673	$1,110.57	$1,110.60	$1,110.50