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	$66.46	10.219%	$73.2515	$73.25	$73.25	$73.30
Purchase #2	$34.76	7.839%	$37.4848	$37.48	$37.50	$37.50
Purchase #3	$167.42	8.612%	$181.8382	$181.84	$181.85	$181.80
Purchase #4	$75.84	6.714%	$80.9319	$80.93	$80.95	$80.90
Purchase #5	$167.45	4.622%	$175.1895	$175.19	$175.20	$175.20
Purchase #6	$77.37	10.444%	$85.4505	$85.45	$85.45	$85.50
Purchase #7	$90.94	8.232%	$98.4262	$98.43	$98.45	$98.40
7 purchase totals =	$680.24		$732.5726	$732.57	$732.65	$732.60