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	$185.88	11.109%	$206.5294	$206.53	$206.55	$206.50
Purchase #2	$247.58	13.296%	$280.4982	$280.50	$280.50	$280.50
Purchase #3	$241.96	9.592%	$265.1688	$265.17	$265.15	$265.20
Purchase #4	$45.54	7.236%	$48.8353	$48.84	$48.85	$48.80
Purchase #5	$60.53	7.743%	$65.2168	$65.22	$65.20	$65.20
Purchase #6	$243.81	4.669%	$255.1935	$255.19	$255.20	$255.20
Purchase #7	$67.92	10.308%	$74.9212	$74.92	$74.90	$74.90
7 purchase totals =	$1,093.22		$1,196.3632	$1,196.37	$1,196.35	$1,196.30