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	$40.79	13.830%	$46.4313	$46.43	$46.45	$46.40
Purchase #2	$194.73	8.278%	$210.8497	$210.85	$210.85	$210.80
Purchase #3	$131.95	3.869%	$137.0551	$137.06	$137.05	$137.10
Purchase #4	$195.51	9.438%	$213.9622	$213.96	$213.95	$214.00
Purchase #5	$16.60	12.114%	$18.6109	$18.61	$18.60	$18.60
Purchase #6	$196.59	10.640%	$217.5072	$217.51	$217.50	$217.50
Purchase #7	$242.68	3.339%	$250.7831	$250.78	$250.80	$250.80
7 purchase totals =	$1,018.85		$1,095.1995	$1,095.20	$1,095.20	$1,095.20