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	$152.57	7.636%	$164.2202	$164.22	$164.20	$164.20
Purchase #2	$107.81	4.141%	$112.2744	$112.27	$112.25	$112.30
Purchase #3	$159.93	11.303%	$178.0069	$178.01	$178.00	$178.00
Purchase #4	$124.47	10.162%	$137.1186	$137.12	$137.10	$137.10
Purchase #5	$89.39	8.272%	$96.7843	$96.78	$96.80	$96.80
Purchase #6	$60.75	3.352%	$62.7863	$62.79	$62.80	$62.80
Purchase #7	$236.40	8.381%	$256.2127	$256.21	$256.20	$256.20
7 purchase totals =	$931.32		$1,007.4034	$1,007.40	$1,007.35	$1,007.40