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	$249.59	4.195%	$260.0603	$260.06	$260.05	$260.10
Purchase #2	$128.73	8.379%	$139.5163	$139.52	$139.50	$139.50
Purchase #3	$27.29	8.293%	$29.5532	$29.55	$29.55	$29.60
Purchase #4	$224.84	11.397%	$250.465	$250.47	$250.45	$250.50
Purchase #5	$40.74	11.370%	$45.3721	$45.37	$45.35	$45.40
Purchase #6	$245.36	6.491%	$261.2863	$261.29	$261.30	$261.30
Purchase #7	$65.61	9.745%	$72.0037	$72.00	$72.00	$72.00
7 purchase totals =	$982.16		$1,058.2569	$1,058.26	$1,058.20	$1,058.40