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	$164.34	8.666%	$178.5817	$178.58	$178.60	$178.60
Purchase #2	$205.97	7.325%	$221.0573	$221.06	$221.05	$221.10
Purchase #3	$114.28	11.620%	$127.5593	$127.56	$127.55	$127.60
Purchase #4	$115.94	13.406%	$131.4829	$131.48	$131.50	$131.50
Purchase #5	$51.53	11.496%	$57.4539	$57.45	$57.45	$57.50
Purchase #6	$152.94	4.853%	$160.3622	$160.36	$160.35	$160.40
Purchase #7	$204.85	11.111%	$227.6109	$227.61	$227.60	$227.60
7 purchase totals =	$1,009.85		$1,104.1082	$1,104.10	$1,104.10	$1,104.30