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	$173.27	3.462%	$179.2686	$179.27	$179.25	$179.30
Purchase #2	$75.30	13.836%	$85.7185	$85.72	$85.70	$85.70
Purchase #3	$193.27	11.561%	$215.6139	$215.61	$215.60	$215.60
Purchase #4	$156.72	7.756%	$168.8752	$168.88	$168.90	$168.90
Purchase #5	$63.64	13.283%	$72.0933	$72.09	$72.10	$72.10
Purchase #6	$129.28	9.217%	$141.1957	$141.20	$141.20	$141.20
Purchase #7	$184.52	7.134%	$197.6837	$197.68	$197.70	$197.70
7 purchase totals =	$976.00		$1,060.4489	$1,060.45	$1,060.45	$1,060.50