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	$135.55	9.156%	$147.961	$147.96	$147.95	$148.00
Purchase #2	$101.38	4.149%	$105.5863	$105.59	$105.60	$105.60
Purchase #3	$242.63	5.172%	$255.1788	$255.18	$255.20	$255.20
Purchase #4	$168.86	12.842%	$190.545	$190.55	$190.55	$190.50
Purchase #5	$190.41	11.504%	$212.3148	$212.31	$212.30	$212.30
Purchase #6	$47.80	4.482%	$49.9424	$49.94	$49.95	$49.90
Purchase #7	$233.33	11.409%	$259.9506	$259.95	$259.95	$260.00
7 purchase totals =	$1,119.96		$1,221.4789	$1,221.48	$1,221.50	$1,221.50