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	$230.97	5.685%	$244.1006	$244.10	$244.10	$244.10
Purchase #2	$28.80	3.799%	$29.8941	$29.89	$29.90	$29.90
Purchase #3	$220.43	3.645%	$228.4647	$228.46	$228.45	$228.50
Purchase #4	$124.39	7.299%	$133.4692	$133.47	$133.45	$133.50
Purchase #5	$233.38	10.296%	$257.4088	$257.41	$257.40	$257.40
Purchase #6	$168.60	13.336%	$191.0845	$191.08	$191.10	$191.10
Purchase #7	$62.63	6.119%	$66.4623	$66.46	$66.45	$66.50
7 purchase totals =	$1,069.20		$1,150.8842	$1,150.87	$1,150.85	$1,151.00