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	$152.89	4.105%	$159.1661	$159.17	$159.15	$159.20
Purchase #2	$215.96	10.612%	$238.8777	$238.88	$238.90	$238.90
Purchase #3	$170.82	3.639%	$177.0361	$177.04	$177.05	$177.00
Purchase #4	$51.25	3.186%	$52.8828	$52.88	$52.90	$52.90
Purchase #5	$178.79	12.121%	$200.4611	$200.46	$200.45	$200.50
Purchase #6	$179.72	6.717%	$191.7918	$191.79	$191.80	$191.80
Purchase #7	$148.54	9.125%	$162.0943	$162.09	$162.10	$162.10
7 purchase totals =	$1,097.97		$1,182.3099	$1,182.31	$1,182.35	$1,182.40