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	$64.75	11.568%	$72.2403	$72.24	$72.25	$72.20
Purchase #2	$137.51	13.872%	$156.5854	$156.59	$156.60	$156.60
Purchase #3	$193.73	11.452%	$215.916	$215.92	$215.90	$215.90
Purchase #4	$164.79	11.110%	$183.0982	$183.10	$183.10	$183.10
Purchase #5	$141.85	7.495%	$152.4817	$152.48	$152.50	$152.50
Purchase #6	$117.64	12.253%	$132.0544	$132.05	$132.05	$132.10
Purchase #7	$38.36	3.541%	$39.7183	$39.72	$39.70	$39.70
7 purchase totals =	$858.63		$952.0943	$952.10	$952.10	$952.10