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	$162.80	8.437%	$176.5354	$176.54	$176.55	$176.50
Purchase #2	$38.86	8.870%	$42.3069	$42.31	$42.30	$42.30
Purchase #3	$68.77	3.685%	$71.3042	$71.30	$71.30	$71.30
Purchase #4	$51.48	9.404%	$56.3212	$56.32	$56.30	$56.30
Purchase #5	$185.43	3.493%	$191.9071	$191.91	$191.90	$191.90
Purchase #6	$225.61	7.197%	$241.8472	$241.85	$241.85	$241.80
Purchase #7	$73.87	3.730%	$76.6254	$76.63	$76.65	$76.60
7 purchase totals =	$806.82		$856.8474	$856.86	$856.85	$856.70