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	$157.58	7.129%	$168.8139	$168.81	$168.80	$168.80
Purchase #2	$185.94	5.558%	$196.2745	$196.27	$196.25	$196.30
Purchase #3	$152.61	3.339%	$157.7056	$157.71	$157.70	$157.70
Purchase #4	$175.91	8.160%	$190.2643	$190.26	$190.25	$190.30
Purchase #5	$58.33	9.555%	$63.9034	$63.90	$63.90	$63.90
Purchase #6	$195.28	13.212%	$221.0804	$221.08	$221.10	$221.10
Purchase #7	$43.47	4.151%	$45.2744	$45.27	$45.25	$45.30
7 purchase totals =	$969.12		$1,043.3165	$1,043.30	$1,043.25	$1,043.40