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	$228.26	4.866%	$239.3671	$239.37	$239.35	$239.40
Purchase #2	$122.63	4.680%	$128.3691	$128.37	$128.35	$128.40
Purchase #3	$142.59	9.632%	$156.3243	$156.32	$156.30	$156.30
Purchase #4	$176.73	3.321%	$182.5992	$182.60	$182.60	$182.60
Purchase #5	$32.27	10.595%	$35.689	$35.69	$35.70	$35.70
Purchase #6	$100.39	7.688%	$108.108	$108.11	$108.10	$108.10
Purchase #7	$197.32	13.459%	$223.8773	$223.88	$223.90	$223.90
7 purchase totals =	$1,000.19		$1,074.3340	$1,074.34	$1,074.30	$1,074.40