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	$207.40	7.265%	$222.4676	$222.47	$222.45	$222.50
Purchase #2	$198.53	5.721%	$209.8879	$209.89	$209.90	$209.90
Purchase #3	$134.33	13.508%	$152.4753	$152.48	$152.50	$152.50
Purchase #4	$90.90	8.526%	$98.6501	$98.65	$98.65	$98.70
Purchase #5	$173.87	13.620%	$197.5511	$197.55	$197.55	$197.60
Purchase #6	$215.79	9.284%	$235.8239	$235.82	$235.80	$235.80
Purchase #7	$37.27	4.752%	$39.0411	$39.04	$39.05	$39.00
7 purchase totals =	$1,058.09		$1,155.8970	$1,155.90	$1,155.90	$1,156.00