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	$140.40	8.646%	$152.539	$152.54	$152.55	$152.50
Purchase #2	$114.38	4.424%	$119.4402	$119.44	$119.45	$119.40
Purchase #3	$231.39	7.611%	$249.0011	$249.00	$249.00	$249.00
Purchase #4	$200.52	7.581%	$215.7214	$215.72	$215.70	$215.70
Purchase #5	$181.29	13.340%	$205.4741	$205.47	$205.45	$205.50
Purchase #6	$156.85	11.635%	$175.0995	$175.10	$175.10	$175.10
Purchase #7	$130.76	11.207%	$145.4143	$145.41	$145.40	$145.40
7 purchase totals =	$1,155.59		$1,262.6896	$1,262.68	$1,262.65	$1,262.60