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	$218.93	10.426%	$241.7556	$241.76	$241.75	$241.80
Purchase #2	$245.70	13.721%	$279.4125	$279.41	$279.40	$279.40
Purchase #3	$78.52	6.453%	$83.5869	$83.59	$83.60	$83.60
Purchase #4	$83.85	11.436%	$93.4391	$93.44	$93.45	$93.40
Purchase #5	$178.31	10.179%	$196.4602	$196.46	$196.45	$196.50
Purchase #6	$166.81	3.689%	$172.9636	$172.96	$172.95	$173.00
Purchase #7	$163.64	5.479%	$172.6058	$172.61	$172.60	$172.60
7 purchase totals =	$1,135.76		$1,240.2237	$1,240.23	$1,240.20	$1,240.30