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	$61.89	12.647%	$69.7172	$69.72	$69.70	$69.70
Purchase #2	$65.89	8.657%	$71.5941	$71.59	$71.60	$71.60
Purchase #3	$58.83	7.338%	$63.1469	$63.15	$63.15	$63.10
Purchase #4	$246.83	9.744%	$270.8811	$270.88	$270.90	$270.90
Purchase #5	$72.45	7.494%	$77.8794	$77.88	$77.90	$77.90
Purchase #6	$58.86	9.651%	$64.5406	$64.54	$64.55	$64.50
Purchase #7	$12.58	5.783%	$13.3075	$13.31	$13.30	$13.30
7 purchase totals =	$577.33		$631.0668	$631.07	$631.10	$631.00