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	$22.54	13.472%	$25.5766	$25.58	$25.60	$25.60
Purchase #2	$13.92	5.784%	$14.7251	$14.73	$14.75	$14.70
Purchase #3	$100.71	10.765%	$111.5514	$111.55	$111.55	$111.60
Purchase #4	$234.43	12.411%	$263.5251	$263.53	$263.55	$263.50
Purchase #5	$222.28	12.214%	$249.4293	$249.43	$249.45	$249.40
Purchase #6	$232.69	7.599%	$250.3721	$250.37	$250.35	$250.40
Purchase #7	$86.78	9.146%	$94.7169	$94.72	$94.70	$94.70
7 purchase totals =	$913.35		$1,009.8965	$1,009.91	$1,009.95	$1,009.90