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	$131.70	9.360%	$144.0271	$144.03	$144.05	$144.00
Purchase #2	$240.80	11.476%	$268.4342	$268.43	$268.45	$268.40
Purchase #3	$54.34	7.491%	$58.4106	$58.41	$58.40	$58.40
Purchase #4	$164.54	11.194%	$182.9586	$182.96	$182.95	$183.00
Purchase #5	$44.84	7.598%	$48.2469	$48.25	$48.25	$48.20
Purchase #6	$243.72	4.798%	$255.4137	$255.41	$255.40	$255.40
Purchase #7	$77.48	10.785%	$85.8362	$85.84	$85.85	$85.80
7 purchase totals =	$957.42		$1,043.3273	$1,043.33	$1,043.35	$1,043.20