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	$163.56	5.568%	$172.667	$172.67	$172.65	$172.70
Purchase #2	$89.86	10.598%	$99.3834	$99.38	$99.40	$99.40
Purchase #3	$66.59	4.362%	$69.4947	$69.49	$69.50	$69.50
Purchase #4	$249.85	10.651%	$276.4615	$276.46	$276.45	$276.50
Purchase #5	$220.86	3.256%	$228.0512	$228.05	$228.05	$228.10
Purchase #6	$68.66	12.845%	$77.4794	$77.48	$77.50	$77.50
Purchase #7	$172.94	3.183%	$178.4447	$178.44	$178.45	$178.40
7 purchase totals =	$1,032.32		$1,101.9819	$1,101.97	$1,102.00	$1,102.10