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	$89.61	12.651%	$100.9466	$100.95	$100.95	$100.90
Purchase #2	$67.41	5.401%	$71.0508	$71.05	$71.05	$71.10
Purchase #3	$18.57	13.153%	$21.0125	$21.01	$21.00	$21.00
Purchase #4	$121.59	12.183%	$136.4033	$136.40	$136.40	$136.40
Purchase #5	$205.71	7.172%	$220.4635	$220.46	$220.45	$220.50
Purchase #6	$207.59	12.558%	$233.6592	$233.66	$233.65	$233.70
Purchase #7	$163.90	9.457%	$179.4	$179.40	$179.40	$179.40
7 purchase totals =	$874.38		$962.9359	$962.93	$962.90	$963.00