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	$6.89	5.443%	$7.265	$7.27	$7.25	$7.30
Purchase #2	$237.63	10.866%	$263.4509	$263.45	$263.45	$263.50
Purchase #3	$36.52	4.226%	$38.0633	$38.06	$38.05	$38.10
Purchase #4	$211.64	3.333%	$218.694	$218.69	$218.70	$218.70
Purchase #5	$29.49	7.155%	$31.6	$31.60	$31.60	$31.60
Purchase #6	$234.29	3.159%	$241.6912	$241.69	$241.70	$241.70
Purchase #7	$227.71	5.817%	$240.9559	$240.96	$240.95	$241.00
7 purchase totals =	$984.17		$1,041.7203	$1,041.72	$1,041.70	$1,041.90