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	$109.68	5.821%	$116.0645	$116.06	$116.05	$116.10
Purchase #2	$48.47	9.464%	$53.0572	$53.06	$53.05	$53.10
Purchase #3	$168.94	6.838%	$180.4921	$180.49	$180.50	$180.50
Purchase #4	$233.47	3.746%	$242.2158	$242.22	$242.20	$242.20
Purchase #5	$165.73	7.632%	$178.3785	$178.38	$178.40	$178.40
Purchase #6	$37.75	12.519%	$42.4759	$42.48	$42.50	$42.50
Purchase #7	$133.68	4.134%	$139.2063	$139.21	$139.20	$139.20
7 purchase totals =	$897.72		$951.8903	$951.90	$951.90	$952.00