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	$159.63	5.409%	$168.2644	$168.26	$168.25	$168.30
Purchase #2	$39.96	7.782%	$43.0697	$43.07	$43.05	$43.10
Purchase #3	$123.30	13.857%	$140.3857	$140.39	$140.40	$140.40
Purchase #4	$224.59	8.752%	$244.2461	$244.25	$244.25	$244.20
Purchase #5	$229.46	9.293%	$250.7837	$250.78	$250.80	$250.80
Purchase #6	$216.90	8.543%	$235.4298	$235.43	$235.45	$235.40
Purchase #7	$162.45	5.339%	$171.1232	$171.12	$171.10	$171.10
7 purchase totals =	$1,156.29		$1,253.3026	$1,253.30	$1,253.30	$1,253.30