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	$101.90	4.856%	$106.8483	$106.85	$106.85	$106.80
Purchase #2	$90.45	10.111%	$99.5954	$99.60	$99.60	$99.60
Purchase #3	$175.81	10.831%	$194.852	$194.85	$194.85	$194.90
Purchase #4	$216.84	6.665%	$231.2924	$231.29	$231.30	$231.30
Purchase #5	$71.59	13.649%	$81.3613	$81.36	$81.35	$81.40
Purchase #6	$102.56	3.283%	$105.927	$105.93	$105.95	$105.90
Purchase #7	$78.46	6.747%	$83.7537	$83.75	$83.75	$83.80
7 purchase totals =	$837.61		$903.6301	$903.63	$903.65	$903.70