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	$240.76	9.399%	$263.389	$263.39	$263.40	$263.40
Purchase #2	$224.80	13.659%	$255.5054	$255.51	$255.50	$255.50
Purchase #3	$169.54	5.191%	$178.3408	$178.34	$178.35	$178.30
Purchase #4	$106.26	10.225%	$117.1251	$117.13	$117.15	$117.10
Purchase #5	$82.79	9.846%	$90.9415	$90.94	$90.95	$90.90
Purchase #6	$55.25	10.131%	$60.8474	$60.85	$60.85	$60.80
Purchase #7	$128.59	12.697%	$144.9171	$144.92	$144.90	$144.90
7 purchase totals =	$1,007.99		$1,111.0663	$1,111.08	$1,111.10	$1,110.90