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	$62.50	13.335%	$70.8344	$70.83	$70.85	$70.80
Purchase #2	$19.84	12.199%	$22.2603	$22.26	$22.25	$22.30
Purchase #3	$235.81	12.544%	$265.39	$265.39	$265.40	$265.40
Purchase #4	$208.71	6.647%	$222.583	$222.58	$222.60	$222.60
Purchase #5	$212.36	11.721%	$237.2507	$237.25	$237.25	$237.30
Purchase #6	$65.52	9.596%	$71.8073	$71.81	$71.80	$71.80
Purchase #7	$161.58	4.149%	$168.284	$168.28	$168.30	$168.30
7 purchase totals =	$966.32		$1,058.4097	$1,058.40	$1,058.45	$1,058.50