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	$62.41	10.434%	$68.9219	$68.92	$68.90	$68.90
Purchase #2	$109.88	6.173%	$116.6629	$116.66	$116.65	$116.70
Purchase #3	$57.65	3.471%	$59.651	$59.65	$59.65	$59.70
Purchase #4	$87.54	5.777%	$92.5972	$92.60	$92.60	$92.60
Purchase #5	$221.65	6.627%	$236.3387	$236.34	$236.35	$236.30
Purchase #6	$82.32	4.814%	$86.2829	$86.28	$86.30	$86.30
Purchase #7	$102.80	8.336%	$111.3694	$111.37	$111.35	$111.40
7 purchase totals =	$724.25		$771.8240	$771.82	$771.80	$771.90