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	$183.59	10.742%	$203.3112	$203.31	$203.30	$203.30
Purchase #2	$66.48	11.174%	$73.9085	$73.91	$73.90	$73.90
Purchase #3	$201.46	4.840%	$211.2107	$211.21	$211.20	$211.20
Purchase #4	$172.28	10.665%	$190.6537	$190.65	$190.65	$190.70
Purchase #5	$39.45	3.680%	$40.9018	$40.90	$40.90	$40.90
Purchase #6	$117.55	5.289%	$123.7672	$123.77	$123.75	$123.80
Purchase #7	$109.77	12.474%	$123.4627	$123.46	$123.45	$123.50
7 purchase totals =	$890.58		$967.2158	$967.21	$967.15	$967.30