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	$94.31	4.238%	$98.3069	$98.31	$98.30	$98.30
Purchase #2	$142.60	3.813%	$148.0373	$148.04	$148.05	$148.00
Purchase #3	$56.89	10.727%	$62.9926	$62.99	$63.00	$63.00
Purchase #4	$88.89	7.482%	$95.5407	$95.54	$95.55	$95.50
Purchase #5	$156.44	8.584%	$169.8688	$169.87	$169.85	$169.90
Purchase #6	$74.87	3.548%	$77.5264	$77.53	$77.55	$77.50
Purchase #7	$105.82	10.510%	$116.9417	$116.94	$116.95	$116.90
7 purchase totals =	$719.82		$769.2144	$769.22	$769.25	$769.10