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	$59.91	3.126%	$61.7828	$61.78	$61.80	$61.80
Purchase #2	$89.27	9.278%	$97.5525	$97.55	$97.55	$97.60
Purchase #3	$141.43	11.492%	$157.6831	$157.68	$157.70	$157.70
Purchase #4	$235.98	10.258%	$260.1868	$260.19	$260.20	$260.20
Purchase #5	$154.95	6.348%	$164.7862	$164.79	$164.80	$164.80
Purchase #6	$89.73	11.244%	$99.8192	$99.82	$99.80	$99.80
Purchase #7	$7.32	4.360%	$7.6392	$7.64	$7.65	$7.60
7 purchase totals =	$778.59		$849.4498	$849.45	$849.50	$849.50