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	$216.27	8.432%	$234.5059	$234.51	$234.50	$234.50
Purchase #2	$206.81	6.743%	$220.7552	$220.76	$220.75	$220.80
Purchase #3	$149.70	10.617%	$165.5936	$165.59	$165.60	$165.60
Purchase #4	$104.26	7.504%	$112.0837	$112.08	$112.10	$112.10
Purchase #5	$175.42	11.844%	$196.1967	$196.20	$196.20	$196.20
Purchase #6	$71.80	12.212%	$80.5682	$80.57	$80.55	$80.60
Purchase #7	$40.70	4.692%	$42.6096	$42.61	$42.60	$42.60
7 purchase totals =	$964.96		$1,052.3129	$1,052.32	$1,052.30	$1,052.40