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	$247.75	9.359%	$270.9369	$270.94	$270.95	$270.90
Purchase #2	$98.42	5.565%	$103.8971	$103.90	$103.90	$103.90
Purchase #3	$113.69	7.424%	$122.1303	$122.13	$122.15	$122.10
Purchase #4	$147.59	7.561%	$158.7493	$158.75	$158.75	$158.70
Purchase #5	$154.94	8.338%	$167.8589	$167.86	$167.85	$167.90
Purchase #6	$48.42	4.272%	$50.4885	$50.49	$50.50	$50.50
Purchase #7	$239.93	5.800%	$253.8459	$253.85	$253.85	$253.80
7 purchase totals =	$1,050.74		$1,127.9069	$1,127.92	$1,127.95	$1,127.80