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	$154.66	6.572%	$164.8243	$164.82	$164.80	$164.80
Purchase #2	$114.28	11.617%	$127.5559	$127.56	$127.55	$127.60
Purchase #3	$142.56	5.719%	$150.713	$150.71	$150.70	$150.70
Purchase #4	$116.99	12.670%	$131.8126	$131.81	$131.80	$131.80
Purchase #5	$216.52	11.664%	$241.7749	$241.77	$241.75	$241.80
Purchase #6	$131.40	3.544%	$136.0568	$136.06	$136.05	$136.10
Purchase #7	$85.60	9.230%	$93.5009	$93.50	$93.50	$93.50
7 purchase totals =	$962.01		$1,046.2384	$1,046.23	$1,046.15	$1,046.30