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	$155.46	6.476%	$165.5276	$165.53	$165.55	$165.50
Purchase #2	$146.60	5.241%	$154.2833	$154.28	$154.30	$154.30
Purchase #3	$98.98	10.586%	$109.458	$109.46	$109.45	$109.50
Purchase #4	$93.42	9.264%	$102.0744	$102.07	$102.05	$102.10
Purchase #5	$135.90	12.509%	$152.8997	$152.90	$152.90	$152.90
Purchase #6	$142.58	11.705%	$159.269	$159.27	$159.25	$159.30
Purchase #7	$197.40	3.782%	$204.8657	$204.87	$204.85	$204.90
7 purchase totals =	$970.34		$1,048.3777	$1,048.38	$1,048.35	$1,048.50