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	$151.49	5.271%	$159.475	$159.48	$159.50	$159.50
Purchase #2	$226.70	6.567%	$241.5874	$241.59	$241.60	$241.60
Purchase #3	$12.41	5.440%	$13.0851	$13.09	$13.10	$13.10
Purchase #4	$190.72	11.163%	$212.0101	$212.01	$212.00	$212.00
Purchase #5	$35.59	6.827%	$38.0197	$38.02	$38.00	$38.00
Purchase #6	$159.65	9.368%	$174.606	$174.61	$174.60	$174.60
Purchase #7	$161.50	3.740%	$167.5401	$167.54	$167.55	$167.50
7 purchase totals =	$938.06		$1,006.3234	$1,006.34	$1,006.35	$1,006.30