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	$173.48	13.426%	$196.7714	$196.77	$196.75	$196.80
Purchase #2	$170.98	12.626%	$192.5679	$192.57	$192.55	$192.60
Purchase #3	$151.93	5.451%	$160.2117	$160.21	$160.20	$160.20
Purchase #4	$63.30	11.305%	$70.4561	$70.46	$70.45	$70.50
Purchase #5	$116.30	6.508%	$123.8688	$123.87	$123.85	$123.90
Purchase #6	$94.42	5.805%	$99.9011	$99.90	$99.90	$99.90
Purchase #7	$207.49	9.730%	$227.6788	$227.68	$227.70	$227.70
7 purchase totals =	$977.90		$1,071.4558	$1,071.46	$1,071.40	$1,071.60