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	$101.56	10.260%	$111.9801	$111.98	$112.00	$112.00
Purchase #2	$131.50	5.498%	$138.7299	$138.73	$138.75	$138.70
Purchase #3	$167.94	11.720%	$187.6226	$187.62	$187.60	$187.60
Purchase #4	$173.83	7.391%	$186.6778	$186.68	$186.70	$186.70
Purchase #5	$37.74	6.569%	$40.2191	$40.22	$40.20	$40.20
Purchase #6	$35.93	8.172%	$38.8662	$38.87	$38.85	$38.90
Purchase #7	$106.82	4.779%	$111.9249	$111.92	$111.90	$111.90
7 purchase totals =	$755.32		$816.0206	$816.02	$816.00	$816.00