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	$196.30	10.259%	$216.4384	$216.44	$216.45	$216.40
Purchase #2	$12.83	7.124%	$13.744	$13.74	$13.75	$13.70
Purchase #3	$145.55	4.246%	$151.7301	$151.73	$151.75	$151.70
Purchase #4	$222.40	10.866%	$246.566	$246.57	$246.55	$246.60
Purchase #5	$194.97	8.450%	$211.445	$211.45	$211.45	$211.40
Purchase #6	$83.78	8.405%	$90.8217	$90.82	$90.80	$90.80
Purchase #7	$142.43	5.405%	$150.1283	$150.13	$150.15	$150.10
7 purchase totals =	$998.26		$1,080.8735	$1,080.88	$1,080.90	$1,080.70