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	$122.32	3.836%	$127.0122	$127.01	$127.00	$127.00
Purchase #2	$229.87	5.359%	$242.1887	$242.19	$242.20	$242.20
Purchase #3	$77.27	6.721%	$82.4633	$82.46	$82.45	$82.50
Purchase #4	$246.79	10.405%	$272.4685	$272.47	$272.45	$272.50
Purchase #5	$113.41	5.238%	$119.3504	$119.35	$119.35	$119.40
Purchase #6	$92.72	9.658%	$101.6749	$101.67	$101.65	$101.70
Purchase #7	$96.80	8.234%	$104.7705	$104.77	$104.75	$104.80
7 purchase totals =	$979.18		$1,049.9285	$1,049.92	$1,049.85	$1,050.10