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	$48.41	6.292%	$51.456	$51.46	$51.45	$51.50
Purchase #2	$153.69	11.448%	$171.2844	$171.28	$171.30	$171.30
Purchase #3	$170.47	10.517%	$188.3983	$188.40	$188.40	$188.40
Purchase #4	$130.85	5.389%	$137.9015	$137.90	$137.90	$137.90
Purchase #5	$233.81	4.605%	$244.577	$244.58	$244.60	$244.60
Purchase #6	$159.40	12.357%	$179.0971	$179.10	$179.10	$179.10
Purchase #7	$120.46	6.743%	$128.5826	$128.58	$128.60	$128.60
7 purchase totals =	$1,017.09		$1,101.2969	$1,101.30	$1,101.35	$1,101.40