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	$153.76	9.483%	$168.3411	$168.34	$168.35	$168.30
Purchase #2	$92.87	13.434%	$105.3462	$105.35	$105.35	$105.30
Purchase #3	$54.32	13.676%	$61.7488	$61.75	$61.75	$61.70
Purchase #4	$96.75	8.581%	$105.0521	$105.05	$105.05	$105.10
Purchase #5	$136.49	6.835%	$145.8191	$145.82	$145.80	$145.80
Purchase #6	$97.76	3.864%	$101.5374	$101.54	$101.55	$101.50
Purchase #7	$55.51	11.335%	$61.8021	$61.80	$61.80	$61.80
7 purchase totals =	$687.46		$749.6468	$749.65	$749.65	$749.50