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	$183.28	12.333%	$205.8839	$205.88	$205.90	$205.90
Purchase #2	$112.53	5.212%	$118.3951	$118.40	$118.40	$118.40
Purchase #3	$27.61	13.110%	$31.2297	$31.23	$31.25	$31.20
Purchase #4	$54.65	13.490%	$62.0223	$62.02	$62.00	$62.00
Purchase #5	$229.37	7.533%	$246.6484	$246.65	$246.65	$246.60
Purchase #6	$141.54	6.584%	$150.859	$150.86	$150.85	$150.90
Purchase #7	$141.84	9.365%	$155.1233	$155.12	$155.10	$155.10
7 purchase totals =	$890.82		$970.1617	$970.16	$970.15	$970.10