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	$97.52	10.359%	$107.6221	$107.62	$107.60	$107.60
Purchase #2	$226.57	12.382%	$254.6239	$254.62	$254.60	$254.60
Purchase #3	$91.59	3.594%	$94.8817	$94.88	$94.90	$94.90
Purchase #4	$160.31	4.412%	$167.3829	$167.38	$167.40	$167.40
Purchase #5	$65.81	9.422%	$72.0106	$72.01	$72.00	$72.00
Purchase #6	$9.88	6.442%	$10.5165	$10.52	$10.50	$10.50
Purchase #7	$43.70	3.868%	$45.3903	$45.39	$45.40	$45.40
7 purchase totals =	$695.38		$752.4280	$752.42	$752.40	$752.40