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	$99.28	12.643%	$111.832	$111.83	$111.85	$111.80
Purchase #2	$103.33	11.652%	$115.37	$115.37	$115.35	$115.40
Purchase #3	$175.39	5.106%	$184.3454	$184.35	$184.35	$184.30
Purchase #4	$178.79	6.752%	$190.8619	$190.86	$190.85	$190.90
Purchase #5	$33.72	9.437%	$36.9022	$36.90	$36.90	$36.90
Purchase #6	$56.79	3.484%	$58.7686	$58.77	$58.75	$58.80
Purchase #7	$198.97	4.661%	$208.244	$208.24	$208.25	$208.20
7 purchase totals =	$846.27		$906.3241	$906.32	$906.30	$906.30