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	$245.25	10.380%	$270.707	$270.71	$270.70	$270.70
Purchase #2	$23.59	10.570%	$26.0835	$26.08	$26.10	$26.10
Purchase #3	$137.74	7.789%	$148.4686	$148.47	$148.45	$148.50
Purchase #4	$190.50	3.268%	$196.7255	$196.73	$196.75	$196.70
Purchase #5	$221.51	8.124%	$239.5055	$239.51	$239.50	$239.50
Purchase #6	$146.38	7.681%	$157.6234	$157.62	$157.60	$157.60
Purchase #7	$52.26	13.419%	$59.2728	$59.27	$59.25	$59.30
7 purchase totals =	$1,017.23		$1,098.3863	$1,098.39	$1,098.35	$1,098.40