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	$242.88	8.700%	$264.0106	$264.01	$264.00	$264.00
Purchase #2	$29.34	10.848%	$32.5228	$32.52	$32.50	$32.50
Purchase #3	$55.50	11.417%	$61.8364	$61.84	$61.85	$61.80
Purchase #4	$238.98	8.416%	$259.0926	$259.09	$259.10	$259.10
Purchase #5	$138.38	4.242%	$144.2501	$144.25	$144.25	$144.30
Purchase #6	$55.69	6.152%	$59.116	$59.12	$59.10	$59.10
Purchase #7	$108.74	3.803%	$112.8754	$112.88	$112.90	$112.90
7 purchase totals =	$869.51		$933.7039	$933.71	$933.70	$933.70