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	$184.48	12.181%	$206.9515	$206.95	$206.95	$207.00
Purchase #2	$211.93	12.530%	$238.4848	$238.48	$238.50	$238.50
Purchase #3	$66.67	8.407%	$72.2749	$72.27	$72.25	$72.30
Purchase #4	$79.59	13.546%	$90.3713	$90.37	$90.35	$90.40
Purchase #5	$192.51	8.228%	$208.3497	$208.35	$208.35	$208.30
Purchase #6	$153.97	13.160%	$174.2325	$174.23	$174.25	$174.20
Purchase #7	$31.63	5.705%	$33.4345	$33.43	$33.45	$33.40
7 purchase totals =	$920.78		$1,024.0992	$1,024.08	$1,024.10	$1,024.10