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	$41.35	3.570%	$42.8262	$42.83	$42.85	$42.80
Purchase #2	$101.42	4.335%	$105.8166	$105.82	$105.80	$105.80
Purchase #3	$72.77	3.629%	$75.4108	$75.41	$75.40	$75.40
Purchase #4	$248.25	13.143%	$280.8775	$280.88	$280.90	$280.90
Purchase #5	$32.39	5.380%	$34.1326	$34.13	$34.15	$34.10
Purchase #6	$222.51	5.485%	$234.7147	$234.71	$234.70	$234.70
Purchase #7	$105.98	6.271%	$112.626	$112.63	$112.65	$112.60
7 purchase totals =	$824.67		$886.4044	$886.41	$886.45	$886.30