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	$179.94	9.405%	$196.8634	$196.86	$196.85	$196.90
Purchase #2	$45.80	10.529%	$50.6223	$50.62	$50.60	$50.60
Purchase #3	$68.26	12.287%	$76.6471	$76.65	$76.65	$76.60
Purchase #4	$208.52	10.452%	$230.3145	$230.31	$230.30	$230.30
Purchase #5	$74.53	7.316%	$79.9826	$79.98	$80.00	$80.00
Purchase #6	$6.98	11.706%	$7.7971	$7.80	$7.80	$7.80
Purchase #7	$248.89	12.726%	$280.5637	$280.56	$280.55	$280.60
7 purchase totals =	$832.92		$922.7907	$922.78	$922.75	$922.80