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	$125.88	4.180%	$131.1418	$131.14	$131.15	$131.10
Purchase #2	$80.73	8.236%	$87.3789	$87.38	$87.40	$87.40
Purchase #3	$186.37	5.418%	$196.4675	$196.47	$196.45	$196.50
Purchase #4	$176.29	9.783%	$193.5365	$193.54	$193.55	$193.50
Purchase #5	$161.67	12.722%	$182.2377	$182.24	$182.25	$182.20
Purchase #6	$39.85	5.743%	$42.1386	$42.14	$42.15	$42.10
Purchase #7	$202.89	10.690%	$224.5789	$224.58	$224.60	$224.60
7 purchase totals =	$973.68		$1,057.4799	$1,057.49	$1,057.55	$1,057.40