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	$116.79	9.391%	$127.7577	$127.76	$127.75	$127.80
Purchase #2	$84.46	9.399%	$92.3984	$92.40	$92.40	$92.40
Purchase #3	$154.72	8.487%	$167.8511	$167.85	$167.85	$167.90
Purchase #4	$48.47	4.374%	$50.5901	$50.59	$50.60	$50.60
Purchase #5	$119.54	10.384%	$131.953	$131.95	$131.95	$132.00
Purchase #6	$221.77	6.145%	$235.3978	$235.40	$235.40	$235.40
Purchase #7	$13.57	9.161%	$14.8131	$14.81	$14.80	$14.80
7 purchase totals =	$759.32		$820.7612	$820.76	$820.75	$820.90