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	$229.76	13.778%	$261.4163	$261.42	$261.40	$261.40
Purchase #2	$51.36	5.194%	$54.0276	$54.03	$54.05	$54.00
Purchase #3	$73.30	13.122%	$82.9184	$82.92	$82.90	$82.90
Purchase #4	$77.76	10.868%	$86.211	$86.21	$86.20	$86.20
Purchase #5	$135.76	4.732%	$142.1842	$142.18	$142.20	$142.20
Purchase #6	$154.25	7.497%	$165.8141	$165.81	$165.80	$165.80
Purchase #7	$247.88	9.428%	$271.2501	$271.25	$271.25	$271.30
7 purchase totals =	$970.07		$1,063.8217	$1,063.82	$1,063.80	$1,063.80