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	$154.50	6.450%	$164.4653	$164.47	$164.45	$164.50
Purchase #2	$226.69	8.322%	$245.5551	$245.56	$245.55	$245.60
Purchase #3	$28.68	12.108%	$32.1526	$32.15	$32.15	$32.20
Purchase #4	$132.92	10.637%	$147.0587	$147.06	$147.05	$147.10
Purchase #5	$79.45	12.257%	$89.1882	$89.19	$89.20	$89.20
Purchase #6	$80.95	13.833%	$92.1478	$92.15	$92.15	$92.10
Purchase #7	$93.42	7.365%	$100.3004	$100.30	$100.30	$100.30
7 purchase totals =	$796.61		$870.8681	$870.88	$870.85	$871.00