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	$231.97	9.750%	$254.5871	$254.59	$254.60	$254.60
Purchase #2	$53.50	10.450%	$59.0908	$59.09	$59.10	$59.10
Purchase #3	$244.43	12.512%	$275.0131	$275.01	$275.00	$275.00
Purchase #4	$139.79	9.760%	$153.4335	$153.43	$153.45	$153.40
Purchase #5	$182.69	11.150%	$203.0599	$203.06	$203.05	$203.10
Purchase #6	$50.58	3.385%	$52.2921	$52.29	$52.30	$52.30
Purchase #7	$150.30	7.810%	$162.0384	$162.04	$162.05	$162.00
7 purchase totals =	$1,053.26		$1,159.5149	$1,159.51	$1,159.55	$1,159.50