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	$250.39	11.109%	$278.2058	$278.21	$278.20	$278.20
Purchase #2	$157.68	4.547%	$164.8497	$164.85	$164.85	$164.80
Purchase #3	$45.83	11.221%	$50.9726	$50.97	$50.95	$51.00
Purchase #4	$184.86	12.559%	$208.0766	$208.08	$208.10	$208.10
Purchase #5	$141.78	11.658%	$158.3087	$158.31	$158.30	$158.30
Purchase #6	$137.41	7.862%	$148.2132	$148.21	$148.20	$148.20
Purchase #7	$86.66	11.762%	$96.8529	$96.85	$96.85	$96.90
7 purchase totals =	$1,004.61		$1,105.4795	$1,105.48	$1,105.45	$1,105.50