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	$163.56	11.532%	$182.4217	$182.42	$182.40	$182.40
Purchase #2	$195.55	8.158%	$211.503	$211.50	$211.50	$211.50
Purchase #3	$120.98	6.542%	$128.8945	$128.89	$128.90	$128.90
Purchase #4	$186.30	4.658%	$194.9779	$194.98	$195.00	$195.00
Purchase #5	$124.49	3.241%	$128.5247	$128.52	$128.50	$128.50
Purchase #6	$142.46	12.634%	$160.4584	$160.46	$160.45	$160.50
Purchase #7	$189.88	4.540%	$198.5006	$198.50	$198.50	$198.50
7 purchase totals =	$1,123.22		$1,205.2808	$1,205.27	$1,205.25	$1,205.30