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	$56.92	4.578%	$59.5258	$59.53	$59.55	$59.50
Purchase #2	$54.50	12.741%	$61.4438	$61.44	$61.45	$61.40
Purchase #3	$146.71	12.137%	$164.5162	$164.52	$164.50	$164.50
Purchase #4	$66.85	11.261%	$74.378	$74.38	$74.40	$74.40
Purchase #5	$168.75	9.343%	$184.5163	$184.52	$184.50	$184.50
Purchase #6	$215.62	4.319%	$224.9326	$224.93	$224.95	$224.90
Purchase #7	$77.43	12.317%	$86.9671	$86.97	$86.95	$87.00
7 purchase totals =	$786.78		$856.2798	$856.29	$856.30	$856.20