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	$160.66	9.615%	$176.1075	$176.11	$176.10	$176.10
Purchase #2	$48.25	11.869%	$53.9768	$53.98	$54.00	$54.00
Purchase #3	$115.55	13.789%	$131.4832	$131.48	$131.50	$131.50
Purchase #4	$237.41	7.603%	$255.4603	$255.46	$255.45	$255.50
Purchase #5	$77.89	3.866%	$80.9012	$80.90	$80.90	$80.90
Purchase #6	$250.69	6.641%	$267.3383	$267.34	$267.35	$267.30
Purchase #7	$49.83	8.780%	$54.2051	$54.21	$54.20	$54.20
7 purchase totals =	$940.28		$1,019.4724	$1,019.48	$1,019.50	$1,019.50