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	$78.45	4.660%	$82.1058	$82.11	$82.10	$82.10
Purchase #2	$49.48	4.123%	$51.5201	$51.52	$51.50	$51.50
Purchase #3	$11.93	8.441%	$12.937	$12.94	$12.95	$12.90
Purchase #4	$181.78	6.593%	$193.7648	$193.76	$193.75	$193.80
Purchase #5	$125.36	6.804%	$133.8895	$133.89	$133.90	$133.90
Purchase #6	$87.85	9.786%	$96.447	$96.45	$96.45	$96.40
Purchase #7	$30.69	13.680%	$34.8884	$34.89	$34.90	$34.90
7 purchase totals =	$565.54		$605.5526	$605.56	$605.55	$605.50