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	$229.72	10.598%	$254.0657	$254.07	$254.05	$254.10
Purchase #2	$81.54	9.206%	$89.0466	$89.05	$89.05	$89.00
Purchase #3	$56.26	7.435%	$60.4429	$60.44	$60.45	$60.40
Purchase #4	$109.94	12.653%	$123.8507	$123.85	$123.85	$123.90
Purchase #5	$118.89	6.848%	$127.0316	$127.03	$127.05	$127.00
Purchase #6	$95.95	10.748%	$106.2627	$106.26	$106.25	$106.30
Purchase #7	$181.56	5.852%	$192.1849	$192.18	$192.20	$192.20
7 purchase totals =	$873.86		$952.8851	$952.88	$952.90	$952.90