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	$218.55	5.507%	$230.5855	$230.59	$230.60	$230.60
Purchase #2	$80.95	11.303%	$90.0998	$90.10	$90.10	$90.10
Purchase #3	$139.69	7.486%	$150.1472	$150.15	$150.15	$150.10
Purchase #4	$106.37	9.657%	$116.6422	$116.64	$116.65	$116.60
Purchase #5	$55.56	5.392%	$58.5558	$58.56	$58.55	$58.60
Purchase #6	$226.64	4.629%	$237.1312	$237.13	$237.15	$237.10
Purchase #7	$184.52	10.205%	$203.3503	$203.35	$203.35	$203.40
7 purchase totals =	$1,012.28		$1,086.5120	$1,086.52	$1,086.55	$1,086.50