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	$117.46	6.199%	$124.7413	$124.74	$124.75	$124.70
Purchase #2	$122.36	3.615%	$126.7833	$126.78	$126.80	$126.80
Purchase #3	$66.94	8.412%	$72.571	$72.57	$72.55	$72.60
Purchase #4	$217.98	10.786%	$241.4913	$241.49	$241.50	$241.50
Purchase #5	$119.58	6.586%	$127.4555	$127.46	$127.45	$127.50
Purchase #6	$202.80	12.173%	$227.4868	$227.49	$227.50	$227.50
Purchase #7	$215.90	13.687%	$245.4502	$245.45	$245.45	$245.50
7 purchase totals =	$1,063.02		$1,165.9794	$1,165.98	$1,166.00	$1,166.10