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	$144.59	12.216%	$162.2531	$162.25	$162.25	$162.30
Purchase #2	$165.35	5.158%	$173.8788	$173.88	$173.90	$173.90
Purchase #3	$137.59	5.714%	$145.4519	$145.45	$145.45	$145.50
Purchase #4	$214.81	12.146%	$240.9008	$240.90	$240.90	$240.90
Purchase #5	$83.50	5.836%	$88.3731	$88.37	$88.35	$88.40
Purchase #6	$203.77	10.848%	$225.875	$225.88	$225.90	$225.90
Purchase #7	$185.52	13.501%	$210.5671	$210.57	$210.55	$210.60
7 purchase totals =	$1,135.13		$1,247.2998	$1,247.30	$1,247.30	$1,247.50