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	$100.86	9.584%	$110.5264	$110.53	$110.55	$110.50
Purchase #2	$47.91	6.625%	$51.084	$51.08	$51.10	$51.10
Purchase #3	$132.54	8.676%	$144.0392	$144.04	$144.05	$144.00
Purchase #4	$53.87	9.259%	$58.8578	$58.86	$58.85	$58.90
Purchase #5	$133.47	6.674%	$142.3778	$142.38	$142.40	$142.40
Purchase #6	$25.88	13.374%	$29.3412	$29.34	$29.35	$29.30
Purchase #7	$67.40	6.105%	$71.5148	$71.51	$71.50	$71.50
7 purchase totals =	$561.93		$607.7412	$607.74	$607.80	$607.70