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	$243.77	11.483%	$271.7621	$271.76	$271.75	$271.80
Purchase #2	$43.45	11.172%	$48.3042	$48.30	$48.30	$48.30
Purchase #3	$45.65	12.779%	$51.4836	$51.48	$51.50	$51.50
Purchase #4	$29.49	7.815%	$31.7946	$31.79	$31.80	$31.80
Purchase #5	$98.37	7.647%	$105.8924	$105.89	$105.90	$105.90
Purchase #6	$119.58	6.530%	$127.3886	$127.39	$127.40	$127.40
Purchase #7	$84.37	11.797%	$94.3231	$94.32	$94.30	$94.30
7 purchase totals =	$664.68		$730.9486	$730.93	$730.95	$731.00