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	$180.49	11.116%	$200.5533	$200.55	$200.55	$200.60
Purchase #2	$40.32	7.658%	$43.4077	$43.41	$43.40	$43.40
Purchase #3	$62.35	7.362%	$66.9402	$66.94	$66.95	$66.90
Purchase #4	$213.52	11.477%	$238.0257	$238.03	$238.05	$238.00
Purchase #5	$183.85	10.426%	$203.0182	$203.02	$203.00	$203.00
Purchase #6	$103.79	7.160%	$111.2214	$111.22	$111.20	$111.20
Purchase #7	$241.79	9.640%	$265.0986	$265.10	$265.10	$265.10
7 purchase totals =	$1,026.11		$1,128.2651	$1,128.27	$1,128.25	$1,128.20