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	$104.89	11.122%	$116.5559	$116.56	$116.55	$116.60
Purchase #2	$77.83	12.364%	$87.4529	$87.45	$87.45	$87.50
Purchase #3	$165.69	12.188%	$185.8843	$185.88	$185.90	$185.90
Purchase #4	$158.25	11.242%	$176.0405	$176.04	$176.05	$176.00
Purchase #5	$44.85	4.847%	$47.0239	$47.02	$47.00	$47.00
Purchase #6	$58.65	6.447%	$62.4312	$62.43	$62.45	$62.40
Purchase #7	$32.85	7.586%	$35.342	$35.34	$35.35	$35.30
7 purchase totals =	$643.01		$710.7307	$710.72	$710.75	$710.70