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	$62.44	3.375%	$64.5474	$64.55	$64.55	$64.50
Purchase #2	$19.79	10.510%	$21.8699	$21.87	$21.85	$21.90
Purchase #3	$158.70	11.112%	$176.3347	$176.33	$176.35	$176.30
Purchase #4	$91.83	7.618%	$98.8256	$98.83	$98.85	$98.80
Purchase #5	$193.56	4.238%	$201.7631	$201.76	$201.75	$201.80
Purchase #6	$57.69	3.617%	$59.7766	$59.78	$59.80	$59.80
Purchase #7	$90.58	5.533%	$95.5918	$95.59	$95.60	$95.60
7 purchase totals =	$674.59		$718.7091	$718.71	$718.75	$718.70