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	$188.44	4.458%	$196.8407	$196.84	$196.85	$196.80
Purchase #2	$27.70	4.643%	$28.9861	$28.99	$29.00	$29.00
Purchase #3	$135.39	5.495%	$142.8297	$142.83	$142.85	$142.80
Purchase #4	$75.51	9.683%	$82.8216	$82.82	$82.80	$82.80
Purchase #5	$232.45	11.424%	$259.0051	$259.01	$259.00	$259.00
Purchase #6	$142.67	4.331%	$148.849	$148.85	$148.85	$148.80
Purchase #7	$83.38	10.733%	$92.3292	$92.33	$92.35	$92.30
7 purchase totals =	$885.54		$951.6614	$951.67	$951.70	$951.50