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	$114.77	11.469%	$127.933	$127.93	$127.95	$127.90
Purchase #2	$14.65	4.315%	$15.2821	$15.28	$15.30	$15.30
Purchase #3	$152.30	6.259%	$161.8325	$161.83	$161.85	$161.80
Purchase #4	$163.96	7.203%	$175.77	$175.77	$175.75	$175.80
Purchase #5	$73.83	8.494%	$80.1011	$80.10	$80.10	$80.10
Purchase #6	$133.78	7.147%	$143.3413	$143.34	$143.35	$143.30
Purchase #7	$178.45	10.191%	$196.6358	$196.64	$196.65	$196.60
7 purchase totals =	$831.74		$900.8958	$900.89	$900.95	$900.80