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	$231.28	7.805%	$249.3314	$249.33	$249.35	$249.30
Purchase #2	$31.69	5.614%	$33.4691	$33.47	$33.45	$33.50
Purchase #3	$185.96	3.311%	$192.1171	$192.12	$192.10	$192.10
Purchase #4	$83.72	8.393%	$90.7466	$90.75	$90.75	$90.70
Purchase #5	$90.87	12.563%	$102.286	$102.29	$102.30	$102.30
Purchase #6	$110.25	9.328%	$120.5341	$120.53	$120.55	$120.50
Purchase #7	$168.55	4.456%	$176.0606	$176.06	$176.05	$176.10
7 purchase totals =	$902.32		$964.5449	$964.55	$964.55	$964.50