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	$221.49	3.664%	$229.6054	$229.61	$229.60	$229.60
Purchase #2	$72.34	11.324%	$80.5318	$80.53	$80.55	$80.50
Purchase #3	$63.96	9.809%	$70.2338	$70.23	$70.25	$70.20
Purchase #4	$72.30	5.178%	$76.0437	$76.04	$76.05	$76.00
Purchase #5	$56.58	10.378%	$62.4519	$62.45	$62.45	$62.50
Purchase #6	$59.61	4.464%	$62.271	$62.27	$62.25	$62.30
Purchase #7	$134.47	7.160%	$144.0981	$144.10	$144.10	$144.10
7 purchase totals =	$680.75		$725.2357	$725.23	$725.25	$725.20