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	$150.96	3.693%	$156.535	$156.54	$156.55	$156.50
Purchase #2	$154.45	13.494%	$175.2915	$175.29	$175.30	$175.30
Purchase #3	$127.69	11.111%	$141.8776	$141.88	$141.90	$141.90
Purchase #4	$209.39	10.593%	$231.5707	$231.57	$231.55	$231.60
Purchase #5	$57.82	7.649%	$62.2427	$62.24	$62.25	$62.20
Purchase #6	$176.94	8.175%	$191.4048	$191.40	$191.40	$191.40
Purchase #7	$40.31	4.271%	$42.0316	$42.03	$42.05	$42.00
7 purchase totals =	$917.56		$1,000.9539	$1,000.95	$1,001.00	$1,000.90