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	$131.33	7.107%	$140.6636	$140.66	$140.65	$140.70
Purchase #2	$164.55	5.155%	$173.0326	$173.03	$173.05	$173.00
Purchase #3	$47.82	11.299%	$53.2232	$53.22	$53.20	$53.20
Purchase #4	$20.44	3.150%	$21.0839	$21.08	$21.10	$21.10
Purchase #5	$162.56	11.707%	$181.5909	$181.59	$181.60	$181.60
Purchase #6	$167.90	8.534%	$182.2286	$182.23	$182.25	$182.20
Purchase #7	$239.38	5.102%	$251.5932	$251.59	$251.60	$251.60
7 purchase totals =	$933.98		$1,003.4160	$1,003.40	$1,003.45	$1,003.40