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	$162.36	13.612%	$184.4604	$184.46	$184.45	$184.50
Purchase #2	$128.68	10.811%	$142.5916	$142.59	$142.60	$142.60
Purchase #3	$62.52	4.687%	$65.4503	$65.45	$65.45	$65.50
Purchase #4	$162.56	9.198%	$177.5123	$177.51	$177.50	$177.50
Purchase #5	$5.96	3.557%	$6.172	$6.17	$6.15	$6.20
Purchase #6	$117.87	10.706%	$130.4892	$130.49	$130.50	$130.50
Purchase #7	$61.56	6.147%	$65.3441	$65.34	$65.35	$65.30
7 purchase totals =	$701.51		$772.0199	$772.01	$772.00	$772.10