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	$161.82	7.333%	$173.6863	$173.69	$173.70	$173.70
Purchase #2	$202.72	9.793%	$222.5724	$222.57	$222.55	$222.60
Purchase #3	$99.65	4.284%	$103.919	$103.92	$103.90	$103.90
Purchase #4	$128.88	8.527%	$139.8696	$139.87	$139.85	$139.90
Purchase #5	$37.30	12.623%	$42.0084	$42.01	$42.00	$42.00
Purchase #6	$215.80	5.355%	$227.3561	$227.36	$227.35	$227.40
Purchase #7	$70.82	9.786%	$77.7504	$77.75	$77.75	$77.80
7 purchase totals =	$916.99		$987.1622	$987.17	$987.10	$987.30