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	$127.47	10.436%	$140.7728	$140.77	$140.75	$140.80
Purchase #2	$223.70	5.353%	$235.6747	$235.67	$235.65	$235.70
Purchase #3	$157.78	13.837%	$179.612	$179.61	$179.60	$179.60
Purchase #4	$250.32	12.153%	$280.7414	$280.74	$280.75	$280.70
Purchase #5	$46.38	12.307%	$52.088	$52.09	$52.10	$52.10
Purchase #6	$128.49	11.228%	$142.9169	$142.92	$142.90	$142.90
Purchase #7	$180.61	8.700%	$196.3231	$196.32	$196.30	$196.30
7 purchase totals =	$1,114.75		$1,228.1289	$1,228.12	$1,228.05	$1,228.10