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	$222.49	7.233%	$238.5827	$238.58	$238.60	$238.60
Purchase #2	$196.69	10.173%	$216.6993	$216.70	$216.70	$216.70
Purchase #3	$164.55	5.326%	$173.3139	$173.31	$173.30	$173.30
Purchase #4	$145.25	13.850%	$165.3671	$165.37	$165.35	$165.40
Purchase #5	$40.81	13.449%	$46.2985	$46.30	$46.30	$46.30
Purchase #6	$153.79	9.173%	$167.8972	$167.90	$167.90	$167.90
Purchase #7	$189.36	3.529%	$196.0425	$196.04	$196.05	$196.00
7 purchase totals =	$1,112.94		$1,204.2012	$1,204.20	$1,204.20	$1,204.20