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	$62.40	8.818%	$67.9024	$67.90	$67.90	$67.90
Purchase #2	$10.32	8.407%	$11.1876	$11.19	$11.20	$11.20
Purchase #3	$58.31	13.299%	$66.0646	$66.06	$66.05	$66.10
Purchase #4	$57.34	9.581%	$62.8337	$62.83	$62.85	$62.80
Purchase #5	$106.32	7.148%	$113.9198	$113.92	$113.90	$113.90
Purchase #6	$110.29	11.477%	$122.948	$122.95	$122.95	$122.90
Purchase #7	$188.42	4.456%	$196.816	$196.82	$196.80	$196.80
7 purchase totals =	$593.40		$641.6721	$641.67	$641.65	$641.60