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	$249.71	3.411%	$258.2276	$258.23	$258.25	$258.20
Purchase #2	$48.34	10.192%	$53.2668	$53.27	$53.25	$53.30
Purchase #3	$229.58	12.270%	$257.7495	$257.75	$257.75	$257.70
Purchase #4	$103.45	3.648%	$107.2239	$107.22	$107.20	$107.20
Purchase #5	$152.95	3.604%	$158.4623	$158.46	$158.45	$158.50
Purchase #6	$34.90	7.574%	$37.5433	$37.54	$37.55	$37.50
Purchase #7	$178.46	11.603%	$199.1667	$199.17	$199.15	$199.20
7 purchase totals =	$997.39		$1,071.6401	$1,071.64	$1,071.60	$1,071.60