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	$107.84	5.299%	$113.5544	$113.55	$113.55	$113.60
Purchase #2	$30.66	9.192%	$33.4783	$33.48	$33.50	$33.50
Purchase #3	$223.85	4.580%	$234.1023	$234.10	$234.10	$234.10
Purchase #4	$127.45	11.137%	$141.6441	$141.64	$141.65	$141.60
Purchase #5	$119.93	9.541%	$131.3725	$131.37	$131.35	$131.40
Purchase #6	$190.45	9.530%	$208.5999	$208.60	$208.60	$208.60
Purchase #7	$60.83	10.308%	$67.1004	$67.10	$67.10	$67.10
7 purchase totals =	$861.01		$929.8519	$929.84	$929.85	$929.90